TEREBRATULA. 357 



T. cranium, Miiller. 

 Surface smooth, whitish, minutely punctulate. 



Plate L VI I. fig. 11. 



/'< rebratula cranium, Muller, Zool. Dan. Prodromus, p. 249, No. 3006. 



Mont. Trans. Linn. Soc. vol. xi. p. 188, pi. 13, f. 2. — 



Turt. Dithyra Brit. p. 23G. — Fleming, Brit. Animals, 



p. 368; Treatise Mollusc. Anim. pi. 14, f. 49. — Brit. 



arine Conch, p. 126. — Brown, Illust. Conch. G. B. p. 



68, pi. 22, £.10,11, 12.— Loven, Moll. Scandinav. p. 29. 



Anomia cranium, Gmelin, Syst. Nat. p. 3347. — Turt. Conch. Diction, p. 5. — 



Dillw. Recent Shells, vol. i. p. 294 (in part; not synonyms). 



Terebratula vitrca, Fleming (not Born nor Chemn.), Edinb. Encycl. vol. vii. p. 



96, pi. 206, f. 2 ; Philosophy of Zoology, pi. 4, f. 4. 



The shape of the Skull Terebratula is ovate or obovate, 

 being but moderately contracted (yet slightly acuminated) 

 above, and but little arcuated below; the central portion 

 of the ventral margin is occasionally a little straightened. 

 The shell is rather gibbous, smooth, glossy, somewhat 

 diaphanous, and of an uniform squalid white or yellowish 

 horn-colour. The valves are almost equal in convexity, 

 and devoid of either ridge or mesial groove : the larger 

 or upper one is somewhat produced above, slightly re- 

 curved, and obliquely truncated at the tip, displaying a 

 large perforation whose margin is not entire or united. 

 The lower or smaller valve is a little flattened, and the 

 slope of its dorsal edges is decided but not abrupt, and 

 generally more or less convex. The suture or junctional 

 line of the valves is a little, but not particularly sinuous, and 

 quite entire. The cardinal area is indistinct and rounded ; 

 the deltidia are small, linear, and separate. The internal 

 appendage, which is large, extending two-thirds the dis- 

 tance from the cardinal margin, is composed of two lateral 



