APPENDIX. 385 



white, cardinal teeth strong and jagged, lateral teeth remote ; no 

 infra-umbonal cavity. l£...2f . S. America. 



Unio Caffer (t. 21, f. 40), Krauss, Sudaf. p. 18, t. 1, /. 14. 

 Small, ovate-oblong, convex, solid, olivaceous, striated with concentric 

 wrinkles, and marked with 2 obsolete lines that run from the beaks 

 to the front extremity of the straightish ventral edge ; dorsal edges 

 slightly curved ; both extremities rounded ; the anterior side the 

 broader, thrice as long as the posterior; inside pale flesh-colour, 

 pearly; primary teeth 2, the hinder in one of the valves oblique 

 compressed and sulcated, the other obsolete. 1^. Natal. 



Unio involutus (t. 23, f. 19), Benson, MS. Peaked-ovate, not 

 so very inequilateral, compressed in front, swollen in the umbonal 

 region, thin, polished, rather pale green, very obscurely subradiated 

 ventrally with ochre-yellow, rather tinged with blue dorsally, marked 

 with 2 or 3 dark green lines on the anterior slope, partially marked 

 with some close and regular shallow groove-like posterior wrinkles, 

 elsewhere smooth ; ventral edge strongly arcuated and much rising 

 behind, less curved yet almost equally rising in front ; anterior side 

 tapering to a blunt subcentral peak, no umbonal ridge ; hinder dorsal 

 edge nearly straight, scarcely sloping ; umbones swollen, prominent, 

 with a few longitudinal corrugations ; beaks incurved ; nacre silvery ; 

 umbonal cavity ample ; lateral teeth large, laminar, raised, the shorter 

 one very elevated at its extremity. 1-J-...1|-. Assam. In the single 

 specimen described from, there is no cardinal tooth, but the hinge-plate 

 is elevated beneath the umbones. 



Unio ascia (t. 23, f. 20), Benson, MS. Oval- sub trapeziform, in- 

 equilateral, moderately strong, subventricose, glossy, ochraceous olive- 

 colour, with concentric, wrinkles ; ventral and dorsal edges convex, 

 the former rising posteriorly, the latter but little sloping ; anterior 

 extremity very bluntly biangulated; hinder dorsal corner angular; 

 umbonal slope broad, with a few divergent corrugations near the 

 much eroded umbones, divided into 2 distinct concavities by 

 an obscure radiating line ; ligament rather elongated, glue-coloured ; 

 nacre bluish, subiridescent in front; umbonal cavity shallow; 

 teeth laminar, lateral, rather long, no true central ones. Penang. 

 Besides the concentric wrinkles, which are chiefly conspicuous 

 anteriorly, there are minute and subparallel scratches in their 

 intervals. 



Unio velaris (t. 23, f. 42), Benson, MS. Obovate-subtrigonal, 

 oblique, winged, not so very inequilateral, very thin, smooth, sub- 

 cuneiform in convexity, being swollen in front (except the dorsal 

 corner), and compressed behind ; cuticle very thin, with a silky gloss, 

 ochraceous-olive, with a dark green narrow ray or two on the broad 

 concave umbonal slope; ventral edge straightish in the middle, 



2 i 



