MAZATLAN BIVALVES 27 



FAMILY SOLECUETID^. 

 GENUS SOLECTJKTUS, Blainv. 



37. SOLECUETUS AFFINIS, 0. B. Ad. 

 C. B. Ad. Pan. Shells, p. 300, no. 510. 



The author of this species does not point out wherein it dif- 

 fers from its Atlantic analogue, S. Caribseus. The similarities are 

 evident. 



The smallest specimen measures long. '3, lot. '84, alt. '14, 



The largest ' '77, 2'4, "48. 



Hah. Panama, very rare, C. B. Ad. Mazatlan : not common : 



L'pool Col. 



Tablet 86 contains 4 young specimens. 87, 3 adult. 88, 3, 

 lighter colour. 89, 3 with thinner epidermis.* 



38. SOLECUETUS POLITUS, n. s. 



S. t. forma " S. affini " simili, sed subtranslucidd, violaced, extus 



lined fused et lineis albicantibus nonnullis radiatd ; epider- 

 _-....._.. ...... 



mide politissimd, fusco-rubente : iniusnymphiselontjatls, 

 denticulis 1-2 acutis, sinupallii versus umbones maxime arcuato ; 

 callositate ab umbonibus , lined fused exteriore con- 

 veniente, subexpressd decur rente . 



Known at once by the brownish violet colour, glossy epider- 

 mis, and dark ray corresponding with a slightly prominent 

 ridge within. In this respect alone it resembles Machsera. In 

 the pallial sinus, S. affinis is intermediate between politus and 

 violascens : in colour, S. violascens is intermediate : in the pro- 

 longation of the nymphse, S. politus. This species displays 2 

 small distinct muscular impressions between the umbo and the 

 anterior adductor, which is oblong, but well defined : in S. vio- 

 lascens, it tapers off irregularly, uniting with these two : in S. 

 affinis it is irregular, not tapering, uniting with the others which 

 are also irregular. The largest specimen measures long. '48, 

 lot. 1'45, alt. '23. 

 Hob. Mazatlan : 4 specimens found with affinis : ISpool Col. 



Tablet 90 contains the most characteristic specimen. 



* Lower down the coast was found a large specimen which appears a distinct 

 species, and I therefore append a description, and deposit the shell in the B. M. 



SOLECUETFS VIOLASCENS. S. t. "S. affini" simili, sed majore, solida, violas- 

 cente, rugis epidermidis tenuioribus ; nymphis elongatis, sinu pallii versus urn- 

 bones minus arcuato. Long '95, lat. 3 '33, alt. -56. Sab. S. W. Mexico, P. P. C. 



