148 



Cytherea (Callista) laciniata, Stoliczka. 



Plate 17, figures 13 and 13a, and plate 19, figures 4 and 4a. 



Cytherea (^Callista) laciniata, Stoliczka. — Cret. Pelecyp. S. India, p. 174, pi. 7, 



figs. 5-6. 

 Compare Otftherea (Callista) seulpturata, Stol. — Id. p. 173, pi. 7, figs. 7-9. 



Shell convex, inequilateral, very variable in shape; outline trans- 

 versely and broadly ovate, ovately subtrigonal or subquadrangular 

 but always a little longer than high. Beaks moderately lai'ge, slightly 

 elevated in some specimens, but a little depressed in others, approximate, 

 acute, curved inwards and forwards, and placed about half-way between 

 the centre and the anterior margin. Superior border sloping concavely 

 downwards in front and convexly behind; ventral margin forming a 

 broad, semi-ovate curve, or gibbous near the anterior end and straighter 

 or curving more gradually upwards near the posterior. Hinge area 

 small, lanceolate, concavely and rather deeply excavated. Lunule small, 

 narrow, ovate-cordate, and margined by a faintly impressed line. 



Surface polished and concentrically ribbed ; the ribs rounded, and wider 

 than the deep furrows between them ; not obsolete or nearly so on the 

 umbones. 



Pallial sinus deep, subangular, bluntly pointed, and extending to the 

 middle of the shell. Left valve with three divergent teeth besides the 

 sublunular tooth. The two cardinal teeth are short, and nearly transverse 

 to the hinge line ; the lateral tooth is elongated, nearly horizontal, and 

 parallel with the fulcrum, from which it is separated by a narrow and 

 not very deep groove. Right valve without any distinct sublunular 

 tooth. 



N. W. side of Hornby Island, in Division D, a fragment of a left 

 valve; Sucia Islands, in Division A, abundant; J. Eichardson, 1871, 

 1874 and 1815. 



A small, neat and concentrically ribbed species, whose characters 

 appear to be almost exactly the same as those of C. laciniata, described 

 by Stoliczka, though the umbones of the latter shell are said to be 

 nearly smooth, and its lunule is not described as margined by an 

 impressed line. It may be that C. laciniata is only the young shell of 

 C. seulpturata, Stoliczka. The Sucia Island specimens of the present 

 species have the same shape and apparently the same kind of lunule 

 as the Meretrix arata of Grabb, from the Chico group of California, but 

 the surface of M. arata is said to be '' ornamented by regular, con 

 centric, acute impressed lines." 



