mazatlan bivalves 27 



Family SOLECUETID^. 

 G-ENCS SOLECUETUS, Blainv. 



37. SoLECUETUS AFFINIS, C. B. Ad. 



a B. Ad. Pan. ShelU, p. 300, no. 510. 



Tlie author of this species does not point out wlierein it dif- 

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

 evident. 



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



The largest „ „ „ '77, „ 2-4, „ -48. 



S«i.— Panama, very rare, C B. ^cZ.— Mazatlan : not common : 



L'pool Col. 



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

 lighter colour.— 89, 3 with thinner epidermis.* 



88. SoLECUETUS POLITUS, n. s. 



S. t. forma " S. ajfini " simili, sed subtranslucidd, violaced, extns 

 lined fused et lineis albicantihus ttonnuUis radiatd ; epider- 

 mide politissimd, fusco-rubente : intus nymphis elongatis, 

 denticulis 1-2 acutis, simipallii versus umbones maxime arciuito ; 

 callositate ab uinbonibus , lined fused exteriore con- 

 veniente, subexpressd decur rente . 



Kno-wTi at once by the broMTiish 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 i)ro- 

 longation of the nj-mphjc, S. politus. This species displays 2 

 small distinct muscular impressions Ijetween tlie umbo and the 

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

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

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

 are also irregular. The largest specimen measures lomf. "48, 

 lat. 1-45, alt. -23. 



Hab. — Mazatlan : 4 specimens found with affinis : L'pool 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. 

 Col. 



SoLECUBTtJS viotASCENS. S. t. "S.affini" simili, sed majore, solida, violas- 

 cente, ru^is epidermidis tenuioribus ; nymphis elongatis, sinu pallii versus uin- 

 bones minus arcuato. Long '95, lat. 3-33, alt. •He.— JIab. S. W.Mexico, P. P. C. 



