60 MA2ATLAN BIVALVES 



Tablet 248 contains 3 young specimens, dull ash colony 

 slightly rayed, one with slight gape. 249, 1 sp. adolescent, 

 closed, slightly rayed on one val^e, the other mostly dull 

 brown. 250, 1 sp. larger, closed, margin waved. 251, 1 fine 

 adult sp. gaping posteriorly and ventrally. 252, 2 sp. very 

 slightly gaping, rays clouded. 253, 1 do., form undulata, gap- 

 ing nearly all round. 254, 2 do. form and colouring intermedi- 

 ate ; one gapes posteriorly, the other ventrally. 255, 2 pairs 

 and 2 valves, form undulata, large posterior gape. 256, 3 do. 

 valves closed ; of which one is nearly white inside, another of 

 a rich diffused violet. Similar differences of colour may be 

 observed in the other specimens, 



GENUS DOSINIA, Scopoli. 



Dosinia, Scop. Intr. ad Hist. Nat. p. 399, (1777). Desk. 



B. M. Cat. Ven. p. 5. 

 Artemis, Poli, Test. utr. Sic. p. 98, 1. 1. (1791). 



88. DOSINIA ? PONDEROSA, Gray. 



Artemis ponderosa, Gray Anal. (1838), vol. viii. p. 309. Rve. 



Conck. Icon. pi. 1. f. k.Hanl. Descr. Cat. p. 109, pi. 19, 



f. 38.&M0. Thes. Conch, p. 656, no. 3, pi. 140, f. 2. 

 Dosinia ponderosa, Desk. B. M. Cat. Ven. p. 7, no. 5. 

 Cytherea gigantea, Phil. Abbild. Conch. Cyth. p. 33, pi. 7, f. 1. 



p. 9, no. 7. 

 Venus cycloides, B. M. Cat. D'Orb. Moll. p. 67, no. 596. 



A single specimen in beautiful condition, after being referred 

 to D. concentrica (Grulf of Mexico), and D, distans (unknown ; 

 probably Puerto Portrero), was at last doubtfully affiliated to 

 this species by Mr. Cuming. A larger specimen procured 

 since from another dealer, and probably from the same collec- 

 tion, confirms the judgment. It is remarkable for the very 

 orbicular form, slightly angulated beyond the ligament ; deeply 

 cut lunule ; and very regular and distant sulci, not obsolete in 

 the middle, of which, measuring from 1 to 1*5 in. from the 

 umbo, there are only 8. The epidermis is extremely glossy, of 

 a very light straw colour. Long. 1*64, lat. 1*74, alt. '73. 

 Hob. Grulf of California, in sandy mud at low water, Sowerby. 



Peru; Payta, D'Orligny. Mazatlan ; extremely rare; 



L'pool Col. 



Tablet 257 contains the specimen. 



