60 MAZATLAK BIVALVES 



Tablet MS contains 3 yoimg specimens, dull asli coloui', 

 sliglitly rayed, one with sligkt gape.— 249, 1 sp. adolescent, 

 closed, slightly rayed on one valve, the other mostly didl 

 browTi.— 250, i 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 undidata, 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 undvdata, 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). — Desh. 



B. 3f. Cat. Veil. p. 5. 

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



88. Dosinia Pponderosa, Grai/. 



Artemis ponderosa, Gra?/ Anal. (1838), vol. viii. p. S09.— Rce. 

 Conch. Icon. pi. 1. f. ^.Sanl. Bescr. Cat. p. 109, pi. 19, 

 f. ZS.—Sow. Thes. Conch, p. 656, no. 3, pi. 140, f. 2. 



Dosinia ponderosa, Desh. B. M. Cat. Yen. p. 7, no. 5. 



Cytherea gigantea, Phil. Ahhild. 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. coucentrica (Gulf of Mexico), and D. distans (unknown ; 

 probably Puerto Portrero). was at last doubtfully aiiiliated to 

 tliis species by Mr. Cuming. A larger specimen procured 

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

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

 orbicular form, slightly angulated beyond the ligament ; deepl>' 

 cut lunule ; and verv regidar and distant sulci, not obsolete m 

 the midcUe, of which, measuring from 1 to l'5in. from the 

 umbo, there are only 8. The epidermis is extremely gbssy, .^t 

 a very light straw colour. Lo)ig. 1'61, lat. 1"74, alt. "73. 

 JI«i.— Gulf of California, in sandy mud at low water, Sowerby. 



—Peru; Payta, J)' 0/-i ;//«//.— Mazatlan ; extremely rare ; 



L'pool Col. 



Tablet 257 contains the specimen. 



