146 mazatlan bivalves 



Family AYICULID^. 



Genus PINNA Linn. 



The remarkable similarity in form between the young shells 

 of Isognomon and those of this genus, confirms the opinion of 

 Dr. AY. B. Carpenter (Br. Assoc. Eep. 1833, p. 20,) and, Prof. 

 E. Forbes (Br. 3Ioll. vol. ii. p. 250.) that it ranks in the present 

 family. An abundance of large Pinnae, sent in the Liverpool 

 Col., were imfortimately sold off at once to the keeper of a 

 tea garden, where they ma}' be seen built up into the walls, 

 and too much disfigured to allow of the species beiag identi- 

 fied. To add to the confusion, an importation of large Piimaj 

 from New Guinea having reached Liverpool at the same time, 

 were mixed with them, both in the shop, and in the garden 

 walls ; and some have fovmd their way into collections as 

 though from jMazatlan. A similar confusion seems to have 

 attended the Pumae sold in London with the Havre Col., on 

 some of which the attached Vermetidfe, corals, &c. clearly 

 prove that they came from far distant seas. The three follow- 

 ing species are all that can be quoted with certainty as having 

 been found in the JMazatlan boxes. Another species, like P. 

 maura, but remarkable for its extreme breadth and thickness 

 and for the shape of the anterior muscidar impression wliich 

 displays a series of ripples, was sent in the S. W. ^Mexican 

 collection. Some species of this genus alter considerably in 

 the shape of the posterior extremity, as they attain maturit}-. 

 The measurenients are taken as in M5'tilida\ 



200. Pinna mauea, Sotv. 



Proc. Zool. Soc. 1835, p. S4,.— Hani. Descr. Cat. p. 255.— 

 C. B. Ad. Pan. Shells, p. 250, no. 395. 



Adolescent shell dark brown, with about IS rows of irregu- 

 lar scales, here and ihere almost tubular ; dark brown ; pos- 

 terior end produced, margin rather straight, ventral edge 

 smooth, slightly inflated ; hinge line inciu'ved near the umbos : 

 anterior impression bilobed. Long.S'o, lat. i,' o, alt.l'oS. 



Hah. — Panama, in muddy banks, Cuming, — Do^ extremely 

 rare, C. B. Adams. — Mazatlan ; probably common, as Lieut. 

 Belcher (Zool. Journ. vol. iv. p. 362) speaks of the large and 

 dangerous shoals of Pinnic in the harbour, which cut boats 

 with their sharp edges ; L'pool Col. 

 Tablet 669 contains one of the very few specimens saved. 



