98 



individuals of both sexes its length is three-fourths its greatest breadth, or even 

 more ; its depth is half its length ; its surface is, to the naked eye, quite 

 smooth, except for a very fine striae which pass from the side- walls across the 

 postero-lateral borders. 



The cervical groove is distinct but rather superficial ; it disappears 

 altogether just behind the post-orbital crests, at a point in line with the 

 orbital tooth. The regions^gastric, cardiac, and epibranchial — are cpiite well 

 defined ; the small pair of prsecardiac facets are distinct but faint ; the narrow 

 tip of the mesogastric area is distinguishable behind the narrow groove that 

 separates the epigastric crests. 



Front in the adult about a third the greatest lireadth of the carapace, with 

 convergent sides, and only moderately declivous ; its free edge is sharp and 

 Ijroadly bilobed. The fold of the front that is turned in to form the inter- 

 antennular septum and the roof of the antennular fossie has a distinct edge of 

 its own independent of the free sharp edge of the " front " proper. 



Orbits broad ; external orbital tooth blunt and not separated from the 

 lower border of the orbit by a gap as it is in the great majority of species of 

 Potamon. 



Antero-lateral borders of carapace convex, cristiform, smooth, and entire 

 in old individuals, very finely crenulate in younger individuals ; lateral 

 epibranchial tooth well formed but rather Ijlunt. Postero-lateral borders ill 

 defined, convergent. 



Epigastric crests sub-trenchant, sub-crescentic, overlapping and slightly in 

 advance of the post-orbital crests. Post-orbital crests trenchant, sinuous, end- 

 ing in line with, but well behind, the lateral epibranchial tooth. In the groove 

 between the post-orbital crest and the orbital edge there is often a small 

 tubercle which is sometimes scrobiculate. 



The abdomen of the adult male forms a broad-based triangle, owing to the 

 narrowness of the three terminal segments compared with the basal segments ; 

 the 6th segment is nearly as long as broad, and the 7th is slightly longer than 

 broad. 



Basal C-'nd) joint of antennal peduncle short ; the succeeding joints are 

 overlapped by the front. 



The mandibular palp seems to consist of only two distinct joints; the 

 distal joint consists of two lobes, a broad anterior lobe overhanging the 

 mandible anteriorly, and a falciform lobe lying behind the incisor edge of the 

 mandible. 



All the maxillipeds have a strong flagellum to their exopodite. The merus 

 of the external maxillipeds is rudely oblong, its breadth considerably exceeding 

 its length. 



Chelipeds unequal in both sexes ; the merus has crenulate edges and very 

 faint squamiform sm-face-sculpture, but the surface of the other joints is to the 



