80 MAZATLAN BIVALVES 



ventrally. 384, 6 do. rather beaked. 385, 4 do. more trans- 

 verse. 386, 7 do. transverse form, beak not indented. 387, 6 

 do. very transverse and indented. Groups shewing colour. 

 Tablet 388 contains 2 sp. whitish var. normal. 389, 2 do. trans- 

 verse. 390, 2 do. flat. 39.1, 2 do. tumid. 392, 3 sp. yellowish 

 var. normal. 393, 3 do. transverse. 394, 2 do. rounded. 395, 

 1 do. tumid. 396, 3 do. orange var 397, 3 sp. dark var. nor- 

 mal. 398, 3 do. elongated. 399, 3 do. rounded. 400, 3 do. 

 tumid. 401, 3 do. form of A. subimbricata. ^402, 3 sp. broad 

 bands. 403, 3 do. speckled. 404, 3 do. narrow bands. 405, 2 

 do. and a valve, bands very faint. 



Tablet 406 contains 3 sp. strongly rugose. 407, 3 dp. smooth 

 form. 408, 3 do. shewing the inside. In all 130 specimens. 



4 113. ANOMALOCAKDIA SUBIMBRICATA, Sow. 



Venus subimbricata, Proc. Zool. Soc. 1835, p. 21. Wood Su/ppl. 



App. pi. 15, f. 57. Sow. Thes. Condi, p. 711, pi. 154, f. 35-38. 

 Anomalocardia subimbricata, Desk. B. M. Cat. Yen. p. 117, no. 4. 



Only a very few small pairs and some young dead valves 

 were found of this species, which further south is not uncom- 

 mon. These few however exhibited remarkable differences. 

 Sometimes the form was regular, sometimes extremely gibbous. 

 Sometimes the concentric folds were rounded ; sometimes 

 as though the shell was raised at intervals and a fresh shell 

 begun below ; sometimes the radiating ribs were crossed by 

 angular laminae, as in Ch. amathusia and gnidia. In this 

 state it may possibly be the V. cancellata of Menke's *Maz- 

 atlan catalogue (Zeit. f. Mai. 1847, p. 191) ; unless indeed 

 that be a young specimen of one of the species above named, 

 from which it may be told by the extremely minute pallial 

 sinus. Very rarely the concentric ridges scarcely appear in 

 the young shell, in which state it might easily be taken for 

 another species. In one very young specimen, on the other 

 hand, the concentric folds are sharp, while the radiating ribs 

 are nearly evanescent. The largest specimen only measures 

 long. I'M, lat.l'l, alt. '77. 

 Hab. Puerto Portrero, in fine sand, 13 fml Cuming. Acapul- 



co, Sowerby. S. W. Mexico, not uncommon, P. P. C. 



Mazatlan ; extremely rare ; L'pool Col. 



Tablet 409 contains 2 minute valves. 410, 5 valves of various 

 forms. 411, the gibbous specimen. 



