300 TESTACEOUS MOLLUSCA. 



0. Rostrata, Ch. f. 677.— W. t.\ 1 , /. 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 in the 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 lamellae. 1£. New 

 Holland. 



0. Mytiloides. Lam. 21. — (Rump. t. 46, f. 0, 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 lamellae ; 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. Sinuata. 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 Edulis."' 



0. Teapezina. Lam. 23. Transversely ovate, distorted, sub- 

 trapeziform, undulatingly gibbous, whitish ; dorsal edges straightish, 

 toothed internally : hinge small and marginal. \\. New Holland. 



0. Rufa. 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 irregular depressed 

 concentric lamellae : lower valve more or less profound, rufous within, 

 excavated beneath the beak, which is greatly produced. Inside of 



1 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 retained 

 in our catalogues, the shell being practically undefined. 



