APPENDIX. 385 
white, cardinal teeth strong and jagged, lateral teeth remote; no 
infra-umbonal cavity. 14...23. 8. America. 
Unto Carrer (t. 21, f. 40), Krauss, Sudaf. p. 18, t.1, f. 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. 13. Natal. 
Unio rnvouutus (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. 14...15. Assam. In the single 
specimen described from, there is no cardinal tooth, but the hinge-plate 
. ts elevated beneath the umbdbones. 
Unto ascta (t. 23, f. 20), Benson, MS. Oval-subtrapeziform, 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 
imtervals. 
Unto venaris (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, 
21 
