91 



18. Paratelphusa (Barytelphusa) lugubris, Wood-Mason. (Fig. 58.) 



Telplrnxd lugubris, Wood-Mason, Journ. Asiatic Soc, Bengal, XL., 1871. pt. II., p. 197, pi. xii., figs. 5-7. 

 Potamoit {Potamon) lut/iibns, Mary J. Rathbun, Nouv. Archiv. du Museum, (4), VI., 1904, p. 308 (id'i til.). 



Colour in spirit dark brown or bronze, sometimes becoming nearly black ; 

 superficial cuticle sometimes furfuraceous, sometimes thick, adherent, and 

 smooth and shiny. 



Carapace flat or flattish, though the individual regions have a slight con- 

 vexity ; its length sometimes slightly over, sometimes slightly under, three- 

 fomths its greatest breadth, its depth a little less than half its length ; its 

 surface to the naked eye finely and abundantly pitted, with some fine oblique 

 wrinkles just inside the lateral borders ; its regions well defined, but, except 

 for the anterior mesogastric groove and two faint prsecardiac facets, not 

 areolated. 



Cervical groove very broad and deep, running sometimes to, sometimes to 

 a point slightly behind, the lateral epigastric tooth on either side. 



Front in the adult one-fourth, or slightly more or less, the greatest breadth 

 of the carapace, declivous, pitted, or rugulose, with a thick, very obscurely 

 crenulate edge, feebly bilobed. 



Orbits wide ; outer orbital angle broad, low, blunt, sometimes dentiform, 

 sometimes not ; not separated from the lower border of the orbit by any gap. 

 Eyes comparatively small. 



Antero-lateral boi'ders of carapace fairly convex, well defined, but not 

 cristiform, very obscurely crenulate ; from about two-fifths to about half of their 

 extent is in front of the lateral epibranchial tooth, which is always small and 

 is occasionally almost indistinguishable. 



Epigastric crests broad, blunt, rugulose, oblique ; their outer ends are 

 sometimes continuous with the post-orbital crests (though meeting them at an 

 angle) and are sometimes incompletely separated from them by a very vague 

 break. The post-orbital crests are sharpish in their outer half; sometimes they 

 run into the lateral epibranchial denticle without any break, sometimes they 

 are broken into tubercles at their outer end, but can still be traced into the 

 lateral epibranchial denticle. 



The outline of the male abdomen is, as in most Paratelphusce, a broad- 

 based, distally-contracted triangle with broadly-rounded apex ; the 6th segment 

 has convergent, slightly concave sides, and its length is equal to its distal 

 breadth ; the length of the 7th segment is equal to its proximal breadth. 



The mouth-parts agree in all respects with those of P. jacquemontii 

 ( = "Telphusa indica") ; the only noteworthy difference is that in the external 

 maxillipeds the ischial groove is sometimes deeper, and the merus is broader 

 and shorter, with its anterior border more oblique. 



