is not obvious in the other species. The second gnathopod sideplate differs from P. fragilis. P. propinquus material is not sufficiently complete to allow full comparison, but differences from the other two species in the 1st and 2nd gnathopods are quite easily seen from the figures.

Phreatogammarus fragilis (Chilton), 1882. (Figs. 1–34.)

Gammarus fragilis Chilton, 1882. 179; pl. 9, figs. 11–18. Chilton, 1894. 227; pl. 21, figs. 1–25.

Phreatogammarus fragilis (Chilton) Stebbing, 1906 454 Chilton, 1909a 56. Chilton, 1918: 83–84.

Colour in spirit, white. Eyes absent. Pleon segments with fine bristles sparsely along dorsum; each urosome segment with 6 or so strong spines dorsally on posterior margin. Length, 13½ mm.; depth, 3 mm.; width, 2½ mm.

Antennae. First: Length, 11 mm., reaching 3rd peraeon segment. Flagellum much longer than peduncle, of about 60 segments, proximal ones wider than long, distally vice versa, distal margins bristled; accessory flagellum 8-segmented. Peduncle, 1st segment distally and inferiorly spined and setose, length more than 3 times width; 2nd narrower, shorter, width ⅕ length, tufts of 3 or 4 setae distally, on margins and surface, inferior tufts with one or two spines; 3rd distally setose, length twice width, a little more than ¼ length 2nd. Second: Length about 7 mm., reaching ½ along antenna 1 flagellum; flagellum about 35-segmented, not much longer than peduncle. Peduncle, 2nd segment wider than long, glandcone produced ½ along 3rd; 3rd subsquare, inferodistal angle spinose and setose; 4th narrower, width less than ⅙ length, length more than 4 times 3rd; tufts of strong setae and, especially superiorly, spines on margins; 5th slightly shorter, narrower, strong tufts of 2 to 8 strong setae on margins and surface.

Mouthparts Lower Lip: Outer lobes strongly bristled. First Maxillae: Inner plate ovate, distally rounded, outer margin straight, inner convex, fringed by about 20 plumose setae; ⅔ length outer plate, which is squarish, has 9 strong toothed distal spines. Palp longer than outer plate; 1st segment small, subsquare; 2nd as wide, 4 times as long, distally rounded, 8 stout spines distally, a strong single seta below outermost. Second Maxillae: Subequal plates distally rounded with strong distal setae; inner has strong fringe of setae along inner margin distally arcing a little across surface, single plumose seta near outer margin at ⅔; inner surfaces finely bristled proximally. Mandibles: Palp, 1st segment width ⅖ greatest length, several strong setae on inner distal angle; 2nd ½ as long again as 1st; inner margin, distal ⅔ fringed with long strong setae; 3rd with margins slightly convex, distally rounded, ¾ length 2nd, inner margin distal ¾ fringed with short strong plumose setae, several very long fine setae on end, about 10 very long setae singly and paired on surface medially. Right: Cutting edge, upper plate of 4 teeth, lower butterfly-shaped with lateral edges of wings finely incised; spine row of 6 strong, scabrous spines; molar process finely spined and granulose, at outer proximal angle a long strong plumose seta, between molar process and spine row a tuft of very fine plumose setae. Left: Upper plate of 5 teeth, lower of 4; spine row of 7 strong spines with smaller interspersed fine plumose setae; molar process distally and proximally has comparatively long plumose setae developed from process margins. Maxilliped: Inner plate short, distally convex, reaching end of merus; outer margin slightly convex, 5 short strong spines distally, surrounded and masked by long plumose

setae reaching ½ down inner margin, a few surface setae. Outer plate reaching ½ along carpus, distally rounded, convex outer margin has 4 or 5 plumose long setae distally, row of about 19 short stout spines on straight inner margin, a few setae below and alongside them. Basos has several long fine surface setae, inner ½ of distal margin has numerous long fine setae; ischium similar; merus has a few short setae on inner distal angle; inner merus margin as long as ischium, ½ length merus outer margin, distal margin oblique. Carpus width 2/7 length, length twice merus outer margin, 1 to 3 small setae on outer margin at ⅓, inner margin and inner ⅓ of surface and distal margin throughout length have strong field of very long setae on outer face; on inner face 3 transverse rows of 2 to 6 long setae near inner distal angle Propod ¾ length carpus, has 2 inner margins, face between them concave, each strongly fringed with setae, inner face has 2 long setae on convex outer margin at ⅔; long setae on outer distal angle; outer face inner surface is strongly setose. Dactylos strong, ½ propod length, strong terminal nail, inner margin and nail base with several fine setae.

Gnathopods First: Sideplate subsquare, tending to trapezoid; angles rounded except sharp posterodistal one, which has 2 small spines; ventral has several fine setae; posterior straight Basos stout, proximally constricted, width nearly ½ length, several very long fine setae ½ down posterior margin; a few shorter setae on anterodistal angle, transverse series of long setae on posterodistal angle. Ischium subtriangular, posterior margin slightly longer than width and ⅖ basos length; very strong fringe of setae on posterodistal angle. Merus as long, posterior margin slightly convex, distal concave medially with strong fringe of long setae. Carpus subtriangular, length ½ basos, greatest width ⅔ basos length, anterior margin convex, several strong setae on anterodistal angle, 1 or 2 on surface, posterior free margin produced as small lobe between propod and merus: lobe and distal margin with strong fringe of long setae. Propod ovate, anterior margin barely convex, posterior strongly so distally; length ⅓ more than basos, greatest width proximally ¾ basos length; anterior margin has 1 or 2 pairs of small setae, anterior surface has (including distal angle) 6 slightly oblique rows of 2 to 10 long setae; posterior margin has about 6 ranks of long setae proximally, inside these 4 strong spines, remaining ¾ of margin has double row of short stout seta-tipped spines, in all about 40, this region corresponding to palm; a few very short scattered surface setae. Strongly curved dactylos as long as basos. reaching ⅔ along propod posterior margin, inner margin toothed throughout, about 8 surface groups of 2 or 3 fine setae. Second: Sideplate as wide as deep; lateral margins straight, rounding regularly to convex ventral margin, ventral and posterior with fine setae. Other segments as in Gn. 1, except: Basos length 3 times width, anterior margin has long fine setae regularly along anterior margin; posterior has very long setae in irregular groups of 2 or 3 proximally, 3 ranks of short setae distally Ischium nearly ¼ basos length, merus not greatly widening distally, length 2/7 basos, anterodistal angle produced as small, blunt boss, Carpus greatest width ½ basos length, barely shorter than basos. Propod greatest width ½ to ⅖ basos length, slightly longer than basos, posterior margin convex proximally and distally, slightly concave where dactylos impinges on palm between ⅓ and ½ along Dactylos ¾ basos length.

Peraeopods First: Sideplate subrectangular, deeper than wide, distal angles rounded, a few setae distally on lateral margins, setae centrally. Gills ovate, reaching ⅔ along basos, subrectangular broodplate as long as basos, nearly as wide.

Basos width less than ⅕ length. margins with long setae proximally, distal ⅔ marginally spined, spines anteriorly slightly the larger. Ischium small, about ⅕ basos length, setae posterodistally. Merus ⅗ basos length, width ¼ length, anterior margin has 4 groups of a few fine setae and usually a single strong spine to each group; posterior has 4 tufts of several fine setae. Carpus width ⅓ length, length ⅔ merus; anterior margin has small tuft of setae at ⅔, similar tuft on angle; posterior has 3 small tufts of setae, distal 2 have small spine each. Propod width ⅕ length, as long as merus; anterior margin has 3 small setae tufts; posterior has 4 groups of 3 or so short strong spines Dactylos stout, about ⅖ propod length, proximal ½ linear, posterior margin then interrupted by 2 small spines, then narrowing sharply to small curved nail. Second: Sideplate wider than deep; angles rounded, ventral margin and angles setose, posterior margin deeply concave proximally so sideplate excavate, otherwise like Pr 1. Third: Broodplate small. There appear to be two gills to each of Pr. 3, 4, 5; a narrow anterior and wide ovate posterior one. Sideplate, anterior lobe slightly the larger and deeper; posterior margin of posterior has 3 strong spines; anterior lobe has several setae ventrally. Basos ovate, narrowing distally, greatest width ½ length; slightly convex anterior margin has about 9 groups of setae each with single spine; posterior has numerous single setae Shorter than but otherwise like Pr. 4, 5. Fourth. Sideplate anterior lobe deeper and much narrower than posterior, ventral margin no more than rounded angle; anterior margin has 4 spines proximally and a few single setae, posterior lobe, ventral margin rounding to posterior which has 3 stout spines Basos posterior margin has small spines replacing setae of Pr. 3; otherwise like Pr 5, but shorter. Fifth: Sideplate anterior lobe the larger, ovate, 2 spines on anterior and 3 on posterior margin; posterior lobe small, sub-rectangular, posterior margin has 3 stout spines. Basos ovate, narrowing distally, length more than twice greatest width; anterior margin has about 8 single spines, sometimes 1 or 2 fine setae with spines; anterodistal angle, like ischium, has tuft of several setae; posterior margin serrate, about 14 single spines. Ischium ¼ basos length, subsquare. Merus width less than ⅓ length, length ¾ basos, anterior margin has 4 groups of a few setae plus a strong spine; posterior has 4 groups of 2 spines, some setae, margins indented by spine insertions, distal margin has spine and setae. Propod much the longest segment, slightly narrower than carpus, basos length ⅔ that of propod; propod basically linear, but margins indented by spine groups; anterior margin has 6 groups and posterior 7, each of 3 or more stout spines and setae. Dactylos ¼ propod length, linear most of length, distally narrowing to short curved nail, row of 6 small fine spines on anterior margin preceding nail.

Epimeral Plates Subrectangular, angles rounded, margins slightly convex. First: Posterior margin with 4 strong spines, slightly convex, ventral margin straight. Second As wide as deep, anterior margin straight, others slightly convex, ventral has 3 strong spines anteriorly set in their length from margin, posterior has 9 or 10. Third Wider than deep, 4 spines ventrally, 9 or 10 posteriorly.

Pleopods. Rami longer than peduncles, inner the longer, peduncle may have 1 or 2 spines or setae marginally and on inner distal angle, 2 or 3 strong coupling spines; rami have 16 to 22 plumose segments, shorter outer ramus usually has the more segments.