300 TESTACEOUS MOLLUSCA. 
O. Rosrrata, Ch. f.677.—W. t.11, f. 67.? Elongated and narrow 
when adult, ovate-oblong when young, very solid; dilated and rounded 
at the base ; slightly incurved towards the attenuated beaks (which are 
curved, and, especially the lower one, moderately produced) posteriorly, 
somewhat convex anteriorly ; valves somewhat compressed (the upper 
the more so), covered with close-set imbricated flattened and not curly 
flakes, which are dirty white and usually mottled with smoke-colour ; 
lower valve white, with more or less distinct coarse radiating folds, its 
ventral edge slightly waved. ‘Inside white; scar obovate and violet ; 
edge quite entire: hinge consisting of a prominent callus in one valve, 
fitting into a corresponding ditch-like cavity inthe other; the liga- 
ment dark greenish. 12. N. America. 
O. Excavata. Lam. 20. Longitudinally ovate, thin, very pale 
violet; upper valve the narrower, plano-concave; lower valve the 
larger, very profound, imbricated with depressed lamelle. 13. New 
Holland. 
O. Myrinomes. Lam. 21.—(Rump. t. 46, f. O, copied in Klein, 
t. 8, f. 17.) Elongated (in characteristic specimens mussel-shaped), 
strong, narrowed at the apex, subtruncated or but little rounded at the 
other extremity. Valves of equal length; the upper very convex, 
covered with flattened purplish black lamelle; the lower usually 
attached by its whole surface to the mangrove. Inside pure white ; 
the cardinal denticles large, close, extending down both sides of the 
upper valve, and leaving their impress strongly marked upon the 
lower valve: cartilage-plate triangular, rather large. 4. Zebu, 
Philippines. 
O. Srnvata. Lam. 22. Rounded-ovate, attenuated at the beaks, 
rather flattened, whitish: ventral margin obtusely waved, posterior 
side with 3 sinuses: upper valve not flat. Australia. ‘“ Slightly 
resembling Epuuts.” } 
O. Trapezina. Lam. 23. Transversely ovate, distorted, sub- 
trapeziform, undulatingly gibbous, whitish ; dorsal edges straightish, 
toothed internally: hinge small and marginal. 14. New Holland. 
O. Rura. Lam, 25.—Del. t. 18, f. 2. Longitudinal, strong, 
tapering towards the beaks, dilated towards the ventral margin, in- 
equivalve. Upper valve shallow, rufous, with wregular depressed 
concentric lamelle : lower valve more or less profound, rufous within, 
excavated beneath the beak, which is greatly produced. Inside of 
' An examination of the type at the French Museum proves that 
the characters upon which this species has been founded are purely 
accidental; the name ought, consequently, no longer to be retamed 
in our catalogues, the shell being practically undefined. 
