Hypogean Crustacea Recording Scheme

Species descriptions

Antrobathynella stammerri / Bathynella natans
Proasellus cavaticus
Crangonyx subterraneus
Microniphargus leruthi
Niphargus aquilex
Niphargus fontanus
Niphargus glenniei
Niphargus kochianus kochianus
Niphargus kochianus irlandicus
Niphargus wexfordensis

For accurate identification of specimens see Gledhill, T., Sutcliffe, D.W. &  Williams, W.D., 1993 ‘British freshwater Crustacea Malacostraca: a key with ecological notes’ Freshwater Biological Association, Scientific Publication No. 52.

The table below and the attached key provide a rough guide to the identification of specimens found in the main caving areas of Britain.

» Download Key – PDF-File, 505.3 KB

AREA	NOTES ON ORGANISMS
Peak District, Yorkshire Dales, Northern England, Scotland and mines in North wales	Niphargus species are not likely to be encountered in these systems Gammarus pulex - if the specimen is largish (~10mm) and shrimp-like with eyes present (these might be white like the rest of the animal). Animal is most likely to be white underground but some specimens, especially in cave systems near the entrance, might have a yellow / orange colouration
South Wales	Niphargus fontanus - Shrimp-like white animal without eyes Proasellus cavaticus - Aquatic woodlouse-like animal, white, eyes absent Gammarus pulex might be present in some caves (see note above) and can co-exist with both Niphargus fontanus and Proasellus (e.g. Elm Hole)
Mendips and Forest of Dean	Niphargus fontanus, Proasellus cavaticus and Gammarus pulex; can co-exist (e.g. Barnes Loop in Swildon's Hole)
Devon	Niphargus glenniei - Small (3mm), white shrimp-like animal, without eyes Niphargus aquilex - Larger (8mm), white, shrimp-like animal without eyes, elongate thin body shape Both these species can co-exist (e.g. Rift Cave, Pridhamsleigh Cave)

Antrobathynella stammerri / Bathynella natans

As discussed in the section on hypogean Crustacea ecology, it is now widely believed that only Antrobathynella stammerri exists in Britain and Ireland.  However, future work might find that Bathynella natans does occur in the British Isles and subsequently the early records of Bathynella natans cannot be entirely discounted.

Bathynella natans (drawing from Gledhill et.al. 1993, after Thienemann)

Both Antrobathynella stammerri and Bathynella natans are very small, eyeless crustaceans, approximately 1mm long and 0.1mm in diameter.  They are more or less colourless with long, thin bodies, highly developed to suit the interstitial habitat in which they are generally recorded.  The body is elongate with 14 trunk segments (8 thoracic and 6 abdominal) and the head is longer than broad.  Each of the thoracic limbs, with the exception of the last, is two-branched.  All but the first and last abdominal segments are without appendages.  The 1st antenna is un-branched, the 2nd has a small branch.  The two species are separated by the number of spines (5 – 7 in Bathynella and 4 in Antrobathynella) on the uropodal protopod and the number of teeth (7 in Bathynella and 6 in Antrobathynella) on the mandible.

Bathynellids were first recorded in Britain in 1927, when A.G. Lowndes collected two specimens (recorded as Bathynella natans) from a tub which caught drippings from the roof of one of the tunnels in Pickwick Quarry, one of the bath stone quarries near Corsham, Wiltshire. Bathynella natans has since been recorded from a spring and riverine gravels in Devon; a spring-fed cattle trough in Berkshire; and water pumped from alluvial gravels on the Thames near Pangbourne, Oxfordshire. All modern (post 1960) records have been positively identified as Antrobathynella stammerri and include pools and streams in White Scar and Great Douk caves, Yorkshire; alluvial gravels on the Altquhurbum Burn, a tributary of the River Endrick in Stirlingshire, Scotland; riverine gravels on the River Plym, Devon; the rivers Tees, Lune, Liza, Derwent and Duddon in Cumbria; and the River Flesk in Killarney, the only record from Ireland.  The only recent records since 1985 are from alluvial gravels on the River Skirfare, Yorkshire, the River Lathkill in Derbyshire (both in 2008) and from an artesian borehole in South Devon (2010).  Outside of Britain Antrobathynella stammerri is known from Germany, Austria, Italy, Romania and the Czech Republic. 

Antrobathynella stammeri from the River Skirfare, Yorkshire, Photo courtesy of Mark Dunscombe

Most of the records are from the interstitial habitat and include areas previously glaciated.  Bathynella / Antrobathynella is likely to have survived beneath the ice in sub-glacial refugia.  Bathynellidae are probably widespread in the interstitial of the phreatic or permanent water table.  The recorded distribution in the British Isles is wide but disjunct and it is likely that the bathynellids have been overlooked and under-recorded.

Proasellus cavaticus

In appearance the Asellidae (freshwater Hoglice) look like aquatic woodlice, with Proasellus being easily separated from the epigean Asellus aquaticus and Asellus meridianus by its lack of eyes and pigment.  Asellus occasionally turn up in allogenic streams in caves, washed in from the surface.

In Gledhill et. al. (1993) Proasellus cavaticus is named as Asellus cavaticus.  Henry & Magniez (1970 & also see 1983) split the genus Asellus, raising the sub-genera Proasellus, Dudich, containing the species Asellus cavaticus and Asellus meridianus, and Conasellus, Stammer, containing Asellus communis, to generic level.  This proposal has been widely accepted in Europe.  At the time of the publication of the FBA key there was some debate amongst the authors but it was decided to retain the single genus Asellus (Gledhill pers. comm.).  Most British workers on the hypogean Crustacea use the name Proasellus cavaticus, in line with their European counterparts.

Proasellus cavaticus was first collected from the Town Well at Ringwood, Hampshire by D.E Lucas in 1925.  It is widespread in caves in the Mendips and South Wales but has also been recorded from various interstitial and groundwater sites in southern England and Wales.  These sites include Wilmington near Dartford, West Kent; the Corsham stone quarries, Wiltshire; water cress beds and a borehole in Dorset; Spratts Barn Mine, Oxfordshire; and several springs and rivers in South Wales.

British Proasellus cavaticus have two distinct size morphs.  A smaller form (approx. 4mm to 6mm) is common in the vadose zone of Mendips caves, whilst the larger (approx. 8mm to 11mm) morph is found in the South Wales caves and the phreatic zone of Mendip caves such as Wookey Hole and the Cheddar River Cave.  The Ringwood specimens and those recently collected from a borehole in Dorset are of the larger morph.  It has been suggested that the two morphs might be distinct taxa and an investigation into the DNA of the British and European Proasellus is in progress, under the supervision of Christophe Douady at the University of Lyon.  Initial results have suggested that the DNA of the two British size morphs and their European relatives are identical and that they are in fact one species, as opposed to a group of cryptic species.  However, the largest British specimens appear to be much larger than the European specimens examined at Lyon so far.

Crangonyx subterraneus

Crangonyx subterraneus, together with Niphargus species are members of the Amphipoda and show the typical “shrimp-like” appearance of the group.  Collectively both Crangonyx subterraneus and the Niphargus species are often colloquially known as ‘well shrimps’ or ‘cave shrimps’.

C. subterraneus from the Little Stour River, Kent

C. subterraneus is not easy to separate from Niphargus without microscopic examination.  The main differences are that in the former the gnathopod hands are longer than broad and the telson is only shallowly emarginated posteriorly.  In Niphargus the telson is deeply cleft and the hands are about as broad as long.  Glennie (1953) observed that live Crangonyx subterraneus kept in captivity crawled upright in silt and never swam or lay on their side, unlike live Niphargus.  A similar behavioural difference is exhibited between epigean Crangonyx pseudogracilis and Gammarus pulex.  C. subterraneus is easily separated from C. pseudogracilis (a naturalised species introduced from North America), the only other Crangonyx in Britain, by its lack of eyes and colouration.

C. subterraneus from the Little Stour River, Kent

C. subterraneus was first described by Bate (1859) after examination of specimens collected (along with several niphargids) by the Reverend A. R. Hogan from a well at Ringwood, Hampshire. It has since been recorded from a well at Marlborough, Wiltshire; alluvial gravels in the River Thames at Whitchurch, Oxfordshire; the Waterston cress beds, Dorset; and two caves, Gough’s cave in the Mendips and from the lake in Ogof Pant canol, part of the Ogof Ffynnon Ddu system. Important recent records include those by Paul Wood from the spring head of the Little Stour River in Kent and by Three Valleys Water staff from boreholes and wells in Hertfordshire and Bedfordshire. There is another important recent record from riverine gravels in the Afon Lluestgota (part of the Rheidol catchment) north east of Aberystwyth, sent in by staff from the Environment Agency. This location is well north of the Devensian limit and has important implications for the distribution of the species. However, no specimen was retained for confirmation and there is some doubt over the correct identification.

Outside of Britain Crangonyx subterraneus is known from western and central Europe.

Microniphargus leruthi has specific characters, such as its small size (2mm) and the shape of the mandiblular palp, telson and gnathopods that set it apart from other genera in the family Niphargidae (Karaman & Ruffo, 1986). The third segment of the mandidular palp does not have a fringe of small bristles. The gnathopds are slightly longer than broad and appear rather rectangular. The telson is as long as wide, has a V-notch (as opposed to a cleft / split in other species) to about halfway and each lobe ends in a single spine. Other differences include the pleopods with two branches and the laccinia of the maxilla with a maximum number of seven spines. These features are illustrated in the sketches below.

Niphargus aquilex in Rift Cave, Devon

Niphargus aquilex was first discovered in 1853 by Professor Westwood, who obtained specimens of a subterranean amphipod from a well near Maidenhead, Berkshire. He described them initially as being Niphargus stygius, a species then known from continental Europe. However, in 1855 Schiődte re-examined the material and described them as a new species, Niphargus aquilex.

On average N. aquilex tends to have a more elongated body shape in comparison to other Niphargus and generally most specimens tend to be larger than N. kochianus and N. glenniei. One of the main features that differentiate N. aquilex is the rounded posterodistal angles on epimeral plates 2 and 3. Lateral spines on the telson lobes and an obtuse palmar angle on the propodus of gnathopods 1 and 2 distinguish this species from N. kochianus.

Niphargus aquilex is the commonest British niphargid, occurring in wells, interstitial gravels and other subterranean waters in southern England and Wales. It has been recorded from many locations, mostly south west of a line drawn from the East Coast of Kent to the Wirral Peninsula in Cheshire, with most records being in the south. There are recent records from Lincolnshire and northern Wales, including Anglesey and very old records exist of the species from Hartlepool, County Durham (1893) and Henwick, Worcestershire (1863).  This latter group of locations is north of the Devensian limit and imply that they might have been re-colonised by N. aquilex after the last ice age (see section on hypogean Crustacea ecology). N. aquilex is probably widely distributed in ground water and is liable to be found where this reaches the surface (e.g. springs) (Gledhill et.al., 1993). It has been found in low-lying ground (e.g. from under the Sphagnum moss cover of a mash near Wellington) where the soil-water zone is continuous with the phreatic, or ground-water, zone and it is thought that, in England at least, the species may be beginning to invade the soil-water zone (Glennie, 1953). N. aquilex is occasionally collected whilst kick sampling for benthic macro-invertebrates in rivers and streams and is likely to be widespread in the hyporheic zone of many watercourses. 

N. aquilex is more commonly found in groundwater sites (e.g. wells, springs, aquifers and riverine gravels) than in caves and there are few records from the latter. There are a few old records from caves in South Wales, but (with the possible exception of Paviland Cave) these are thought to be mis-identifications or typographical errors. It is common in Holwell Cave in Devonian Limestone in the Quantock Hills, Somerset and frequently occurs in caves in Devon, also in Devonian Limestone. Holwell Cave and the Devon caves differ from most other British caves in their Devonian geology. However it is thought that the main reason for N. aquilex’s presence in caves in the far south west might be the absence of Niphargus fontanus, the most commonly occurring cavernicolous Niphargus, from this area. Competition with the robust and relatively large N. fontanus might exclude N. aquilex from caves in the Mendips and South Wales, although the two species are often recorded together at groundwater sites such as the Town Well at Ringwood and Waterston cress beds. N. aquilex sometimes occurs with Niphargus glenniei in Devon caves, even sometimes in the same pools. However, N. glenniei is much smaller and less likely to be a competitive threat.

As well as mainland Britain and the Isle of Anglesey mentioned above, Niphargus aquilex has also been recorded from the Isle of Wight and Guernsey in the Channel Islands. It is also known from central and southern Europe, including Italy and the Balkans.

Niphargus fontanus was originally described by Bate (1859) from specimens collected from Ringwood, Hampshire and Corsham, Wiltshire. Since the original description is rather short and poorly illustrated, Gledhill (1980) designated and described the lecotype from one of two syntypes held at the British Museum of Natural History. Niphargus fontanus is differentiated from Niphargus kochianus by lateral spines on the telson lobes and an obtuse palmar angle on the propodus of gnathopods 1 and 2. The propodus of gnathopod 2 is distinctly larger (longer and wider) than that of gnathopod 1, a key distinguishing feature for N. fontanus. Epimera 2 and 3 have a sub-rectangular posterodistal angle.

N. fontanus is known from groundwater sites (including wells, boreholes and interstitial gravels) across southern England and Wales, from Kent in the east, as far north as Cambridgeshire, and Carmarthenshire and Breconshire in the west. It is absent from the far south west (Devon and Cornwall). With the exception of South Wales and a few other outlying records, its distribution is mostly concentrated south of the Devensian limit. N. fontanus is the most cavernicolous (cave-dwelling) of the British niphargids and it is widely recorded from caves in the Mendips and South Wales.

Away from mainland Britain, N. fontanus has also been recorded from two wells on the outskirts of St. Hellier on Jersey. On the continent it is known from eastern France, Belgium, Germany and Austria. 

Specimens of N. fontanus from cave habitats generally tend to be larger and more robust than those from interstitial and phreatic sites. It is not known whether this is a physiological response to the smaller spaces in groundwater habitats or to the fact that food sources might be more available in cave habitats. DNA analysis is currently being undertaken on specimens from different habitats to detect if there might be cryptic taxa present.

Niphargus glenniei was first observed on 19th April 1948 in Pridhamsleigh Cave, near Buckfastleigh, Devon by Brigadier E.A. Glennie of the Cave Research Group, in company with Mary Hazleton, who actually captured the first specimen. G.M. Spooner, of the Plymouth Marine Laboratory examined these first specimens and described them as a new species (Spooner, 1952) named after Glennie himself.

Niphargus glenniei can usually be easily separated from the other British adult niphargids by virtue of its much smaller size. Niphargus glenniei attains sexual maturity at 2.5 to 4mm long (most specimens tend to be 3mm in size), whilst other British Niphargus species are sexually mature at a minimum size of 4 to 6mm (most specimens found tend to be at least 8mm, with some up to 15mm in length). The Irish species, Niphargus wexfordensis, is the nearest species from the British Isles to Niphargus glenniei in size, attaining sexual maturity at 4.5mm. Other distinguishing features are the lack of spines on the telson lobes; rounded palmar angles on the gnathopods (gnathopod 2 propodus larger than that of gnathopod 1); a reduced number of D-setae on mandible palp article 3; and on uropods 1 and 2 the outer ramus is distinctly shorter than the inner ramus. This latter feature is probably the easiest to see under a microscope and is the most obvious way of identifying the species.

N. glenniei in Reed's Cavern, Buckfastleigh, Devon

Schellenberg (1938) established the genus Niphargellus, containing the European species Niphargellus arndti and Niphargellus nolli, primarily on the basis of reduced setation of the mandibular palp. Although Spooner (1952) and others considered Niphargellus to be invalid, It was retained and some authors (e.g. Glennie, 1967; Gledhill et.al. 1976; Karaman & Ruffo, 1986) formerly placed N. glenniei in Niphargellus. However another species, Niphargus boulangei also has a reduced number of setae, as does the relatively recently discovered Niphargus wexfordensis from Ireland. Karaman et. al. (1994) therefore concluded that the genus Niphargellus should only be retained for Niphargellus arndti and Niphargellus nolli and that the Niphargus glenniei group (including N. boulangei and N. wexfordensis), with low numbers of D-setae, represents a link between the genus Niphargus, with a fringe of numerous D-setae and the genus Niphargellus with no D-setae. Thus N. glenniei is now considered to be a member of the genus Niphargus (Karaman et. al. 1994 and Gledhil et. al. 1993).

N. glenniei from Fishcombe Quarry Cave, Brixham, Devon. Photo courtesy of Chris Proctor

Glennie (1967) states that "Niphargus glenniei is a highly interstitial form", as suggested by its thin body and small size and that the species is "frequent in the Pridhamsleigh and Buckfastleigh caves in the Devonian limestones in South Devon, where its true home is in the very disturbed rock."

Until recently, the county of Devon was thought to be the only locality world-wide from which Niphargus glenniei is known. It is believed to be endemic to England and was given a Red Data Book K and 5 (Insufficiently Known and Endemic) conservation status by Bratton (1992). It has recently (2007) been accepted on the list of British Biodiversity Action Plan (BAP) species and in addition to the Devon BAP, is on the local BAPs for the Torbay, Teignbridge and Dartmoor areas, which include some of the caves and wells in which it occurs.

N. glenniei from Fishcombe Quarry Cave, Brixham, Devon. Photo courtesy of Chris Proctor

Within Devon it has been recorded from Napps Cave, near Berrynarbor in the north of the county and more recently (2010 and 2009) from a well near Mortehoe and a spring, well and borehole near Tiverton.  However, by far the majority of the records are in the south of the county and include a spring issuing through metamorphosed slate at Moortown, near Tavistock; a spring-fed well in the Haldon Hills; superficial riverine gravels in a spit on the upper reaches of the River Plym; and wells at Moorgate and Kenton.  Most of the records are from caves and some mines, with recent (post 1998) discoveries in the Chudleigh, Torquay and Brixham Devonian limestone outcrops.

In late 2000, N. glenniei was discovered in a well in granite near Land’s End and recent investigations have found the species at three other wells in West Cornwall, as far east as Falmouth. It is very likely that N. glenniei is widespread in the phreatic groundwater between West Cornwall and the Devon border.

First described by Bate (1859) as Niphargus kochianus from a single specimen collected from a pump in a house at Ringwood, Hampshire. Schellenberg (1933) added two sub-species, one from Belgium and France and one from Ireland (Niphargus kochianus irlandicus), upon examination of the first male specimens obtained. British specimens of male Niphargus kochianus kochianus were not recorded until 1970, from the Waterston cress beds by Gledhill. It is thought that the hitherto rarity of the males was due to the dominance of females in most collections and the fact that the two sexes are very similar morphologically. Sexual dimorphism is not evident in the uropods, as it is in most niphargids, but in the length of the carpus of the gnathopods. Males are also on average smaller, the reverse being true for most other gammarids. These newly discovered British males differed from the descriptions of European male Niphargus kochianus kochianus and it was thought that the European specimens might actually belong to a different sub-species. Stock & Gledhill (1977) revised the taxonomy of the Niphargus kochianus group in North West Europe. Specimens from the Netherlands and Belgium, previously thought to be Niphargus kochianus kochianus, were re-designated as a new sub-species, Niphargus kochianus dimorphopus, based on the pronounced sexual dimorphism of the male’s second pair of gnathopods, which is feeble in N. kochianus kochianus. Another sub-species N. kochianus pachypus was also re-described and raised to species rank. Stock & Gledhill (1977) and Karaman & Ruffo (1986) consider N. kochianus kochianus to be endemic to southern England, though Vonk (1988) and Ginet (1996) record it from France. Other members of the Niphargus kochianus group (N. kochianus dimorphopus, N. kochianus petrosan, N. kochianus polonicus and N. pachypus) are recorded throughout Europe, from the Netherlands to Romania and Russia.

N. kochianus kochianus is differentiated from other British niphargids by the sub-acute palmar angle of the propodus of gnathopods 1 and 2 and the acute posterodistal angle of epimeron 3. The telson lobes lack lateral spines, although 3 - 4 distal spines are present. N. kochianus kochianus and N. kochianus irlandicus primarily differ in the shape of the propodus; an extensive fringe of D-setae on the mandible palp article 3 of N. kochianus irlandicus; a single dorsal spine on either side of urosome segment 2 in N. kochianus kochianus (3 – 4 spines in N. kochianus irlandicus); and the more acute posterodistal angle on epimeron 3 in N. kochianus kochianus.

N. kochianus kochianus from the lake in Pen Park Hole, Bristol

N. kochianus kochianus has been recorded across southern England, from Norfolk and Kent in the east to Gloucestershire (possibly Somerset?) and Dorset in the west. It is absent from Devon and Cornwall.  There is also a single record from Jersey in 1960. There appears to be a strong correlation between the chalk (Cretaceous Limestone) outcrops and the distribution of N. kochianus kochianus. A similar association has been reported by Vonk (1988) in France. Most of the records are from interstitial (alluvial gravels) and phreatic (boreholes and wells) sites with only three records from caves. The single 1966 record from St. Cuthbert’s Swallet, in the Mendips is thought to be a possible confusion with mis-identified Niphargus fontanus. There are two 1951 records from Holwell Cave in the Quantock Hills of Somerset, although recent visits have only found Niphargus aquilex. Niphargus kochianus kochianus is present in large numbers, sometimes accompanied by N. fontanus, in the lake in Pen Park Hole, Bristol. This has been confirmed by recent surveys. The lake is believed to connect to the phreatic water table and the level has been observed to fluctuate with groundwater levels. It is thought that N. kochianus kochianus is predominately an inhabitant of phreatic groundwater.

N. kochianus irlandicus

N. kochianus irlandicus has been recorded from numerous localities across southern and central Ireland, extending from County Kerry and County Cork in the south, as far north as the Dundalk Peninsula (County Louth) on the east coast and the high plateau above the village of Geevagh (County Sligo) in the west. The County Sligo record, from the Carrowmore cave system is the most northerly for the genus Niphargus in Europe. Unlike most other British niphargids, most of these records are within areas fully glaciated during the Midlandian. Costello (1993) suggests that it might be a pre-glacial relict species, having survived beneath the ice in sub-glacial refugia. Habitats that N. kochianus irlandicus has been recorded from include springs, wells, riverine gravels and caves, the latter mostly in County Clare. It has also been recorded in the bottom sediments of Lough Mask. Both Schellenberg (1932) and Stock & Gledhill (1977) noted slight morphological differences between specimens from Lough Mask and those from caves and wells, although these were not thought sufficient enough to form the basis of a new taxon. However, in light of the new DNA evidence separating N. kochianus irlandicus from N. kochianus kochianus, some new research into this subject is required. Extensive surveys of the Irish hypogean Crustacea were carried out in 2006 and 2008, with further work planned in 2009 to 2011.

N. wexfordensis (drawing from Karman et. al., 1994 'A new subterranean amphipod (Crustacea: Gammaridea: Niphargidae) from southern Ireland, with comments on itas taxonomic position and the validity of the genus Niphargellus Schellenberg.' Zoological Journal of the Linnean Society, 112)

First recorded from a well in the garden of a house at Kerloge, County Wexford in 1980, this was the only known location for this endemic Irish species until 2006, when it was discovered at a second site in County Wexford by Dr. J. Arnscheidt of the University of Ulster. It has since been discovered at another four sites in a recent survey of Irish sygobitic Crustacea in springs and caves carried out by Ecoserve and L. Knight in 2008. These sites included a spring in County Wexford; a spring in County Kilkenny; Central Cave, in the Carrigacrump Quarry, County Cork; and Polldubh Cave on the Burren, County Clare. N. kochianus irlandicus was also recorded with N. wexfordensis in the Kilkenny spring and Central Cave. The results of this survey led to the re-examination of specimens, identified as Niphargus kochianus irlandicus, collected from the Doolin River Cave (Co. Clare) in 2005 and the discovery that one of the smaller specimens was actually Niphargus wexfordensis.  Further work in March 2009 found N. wexfordensis in a third cave on the Burren (Doonyvarden Cave), along with Microniphargus. These records show that N. wexfordensis is more widespread than previously thought and also raises some questions on the identity of some of the records in the 1960s and 70s from caves on the Burren. At the time N. kochianus irlandicus was the only species known to exist in Ireland. At the time N. kochianus irlandicus was the only species known to exist in Ireland.

Niphargus wexfordensis from a spring in County Kilkenny

Niphargus wexfordensis was described by Karaman et. al. (1994), who noted its similarities with Niphargus glenniei, primarily a reduced number of D-setae on article 3 of the mandible palp, a small size and the outer ramus distinctly shorter than the inner on uropod 2 (although the rami are sub-equal on uropod 1). It differs from N. glenniei in the telson being cleft to almost half its length (three-quarters in N. glenniei and N. kochianus irlandicus), with each lobe bearing 3 distal spines and a pair of plumose setae (no spines and 3 distal setae in N. glenniei) and differences in the setation of the mandible palp articles 2 and 3. The main features that separate the species from N. kochianus irlandicus include the telson cleft and mandible palp, mentioned above and the more rounded shape of the gnathopods, with gnathopod 2 propodus normally larger than that of gnathopod 1. This latter feature means that superficially N. wexfordensis resembles small specimens of N. fontanus.