NATURAL SCIENCES OF PHILADELPHIA. 213 



This shell somewhat resembles P. p a p y r a c e a in its external markings, 

 but it is narrower, longer, more acuminate posteriorly and the impressed rib 

 more oblique. The form of the cup-shaped appendage is also different. 



P. sulcata, Brown. (Sp.) 



Pholas sulcata, Brown, 111. Conch. Gt. Brit. p. 115, t. 48, f. 17, 18. 

 Pholadidea sulcata, H. and A. Adams, Genera, ii. p. 329. Fischer, Journ. 

 de Conchyl. 2d ser. iii. p. 51. Forbes and Hanley, Brit. Moll. i. 

 p. 128. 

 Hab. England. 



Only a single valve of this shell has been found ; it agrees very nearly 

 with the young of P. p ap y r a c e a, but Capt. Brown is confident of its spe- 

 cific value. 



P. ovoidea, Gould. (Sp.) 



Pholas ovoidea, Gould, Jour. Bost. Soc. N. Hist. vi. p. 388, t. 15, f. 1. 



Parapholas ovoidea, H. and A. Adams, Genera, ii. p. 330. Fischer, Journ. 

 Conch. 2d ser. iii. p. 52. 



Pholadidea ovoidea, Carpenter, Rep. on W. Coast Shells. Carpenter, Zool. 

 Proc. 1856, p. 198. 



Hab. Lower California. 



Coll. A. A. Gould, M. D. 



This species probably belongs in the genus Pholadidea, although its position 

 cannot be accurately determined on account of the loss of its dorsal valves. 

 Its form and sculpture will readily distinguish it from the other species. 



Subgenus Talonella, Gray. 

 Talonella, Gray, Ann. and Mag. Nat. Hist. 2d ser. viii. p. 385, 1851. 



Siphonal valves without any tubular prolongation, and with a longitudinal and 



transverse fold. 

 P. t rid ens, Gray. 



Pholas (Talonella) t r i d e n s, Grav, Brit. Mus. Sowerby, Monog. Pholas, Thes. 

 Conch, ii. p. 498, t. 106, *f. 60, 61. 



Pholadidea t r id ens, Gray, Ann. and Mag. Nat. Hist. 2d ser. viii. p. 385. 

 H. and A. Adams, Genera, ii. p. 329. Fischer, Journ. Conchyl. 2d 

 ser. iii. p. 51. 

 Hab. Monte Christo. 



The form of the cup distinguishes this curious little species from all others. 

 Although so small, the shell is adult, as is evidenced by the presence of the 

 anterior ventral callous plate. 



Subgenus Hatasia, Gray. 

 Hatasia, Gray, Ann. and Mag. Nat. Hist. 2d ser. viii. p. 385, 1851. 



Siphonal valves with a tubular shelly prolongation. 

 1. P. melanura, Sowerby. (Sp.) 



Pholas melanura, Sowerby, Proc. Zool. Soc. p. 70, 1834. Sowerbv, Monog. 



Pholas, Thes. Conch, ii. p. 499, t. 107, f. 78, 79. Catlow, Conch. 



Nomenc. p. 4. Conrad, Journ. Acad. Nat. Sc. 2d ser. ii. p. 335, 1854. 



D'Orbigny, Moll. Voy. Amer. Merid. p. 499. Miiller, Syn. Test. Viv. 



p. 238. 

 Pholadidea melanura, Gray, Ann. and Mag. 2d ser. viii. p. 385. H. and 



A. Adams, Genera, ii. p. 329. Carpenter, Rep. on West Coast Mol- 



lusca. Carpenter, Cat. Mazatlan Shells, p. 8. Chenu, Man. Conch. 



ii. f. 32, 33, Fischer, Journ. Conch. 2d ser. iii. p. 51. 

 18G2.] 



