76 JtAZATlAN BIVALVES 



often purple, especially ou tlie liinge line. The smallest valve 

 is '03 across ; the largest measures long. 1"9, led, 2", alt. 1'28. 



Hah. — St. Elena, Ln coarse sand at low water, Cuming. — 

 Ecuador ; St. Elena, D'Orbigni/.—S. ^Y. Mexico, P. P. C— 

 Mazatlan ; extremely common ; L'pool Sf Havre Coll. 



Tablet 357 contains 7 young valves, [?], limule not defined, 

 very faint concentric lines of growth, anterior tooth elongated, 

 as is usual in young Venendae. 



Tablet 358 contains 7 specimens of the normal chocolate 

 colour. — 359, 7 do. with white umbos. — 360, 7 do. purplish 

 tinge. — 361, 7 do. light coloured, shghtly spotted. — 362, 7 do. 

 with large patches of dark. 



108. Venus (? Chione) , sp. ind. 



Tablet 363 contains 3 small valves, the smallest only '02 

 across, smooth and white, which do not accord with any of the 

 foregoing species. 

 Hah. — Mazatlan ; in shell washings : L'pool Col. 



Genus TAPES, Megerle. 



This genus, though the tjT)e of a sub-family of Gray, (B. M. 

 Cat Yen., p. 159) approaches Venus (Chione, Megerle, Gray.) 

 by insensible gradations. The following species may be ranked 

 with cither genus. The t.^^iical forms have not yet been found 

 in this Zoological province. 



109. Tapes histeionica, Brod. Sj Sow. 



Venus histrionica Proc. Zool. Soe. 1835, p. 41.— Haul. Be.scr. 



Cat. p. 119 ; Wood. Supjjl- pl- 16, f- 31.— 5. M. Cat. D'Orh. 



Moll. p. 07, no. 59L—S0W. Tlies. Conch, p. 714, pi. 55, f. 52. 

 Chione histrionica, Dcsh. B. M. Cat. Yen. p. 139, sp. (50. 

 Tapes histrionica, Hani. Col. suo. 



This belongs to a group of verj- closely allied species, of 

 which T. granulata {B. 31. Cat. Yen. p. 138,) is the W. Indian 

 analogue, and T. straminea the Cahfornian. It has the form 

 and sculpture of a Tapes, Avith the teeth and pallial sinus of a 

 Venus. The form varies in tlie greater or less development of 

 the posterior angle, and in the flattening or rounding of the 



