Dr. J. E. Gray on some Families of Bivalve Shells. 37 



** Hinder cardinal tooth smooth. 

 7. Dione, 8. Venus. 9. Circe. 



b. Anterior lateral teeth none ; cardinal teeth triangular ; shell 



ovate. 



10. Chione (and Mercenaria). 11. Anomalocardia. 



c. Anterior lateral teeth none; cardinal teeth compressed; shell 



oblong. 



12. Tapes (Saxidomus and Rupellaria part.). 13. Clementia. 

 Fam. 2. Cyprinad^. 



Shell ovate, cordate, covered vpith a hard dull brown perios- 

 traca. The hinge-teeth 3 • 3, triangular ; the front of left valve 

 conical, rugose, like the anterior lateral tooth of Venus; the hinder 

 of left valve very thin, compressed ; the middle of right valve 

 compressed ; the hinder very broad, with a deep groove ; anterior 

 lateral tooth none ; hinder of right valve compressed, separated 

 from the dorsal margin by a deep groove. Siphonal inflection 

 noncj or very slightly truncate. Mantle lobes free beneath. 

 Siphons very short (Miiller, Zool. Dan.). 



These shells have much the appearance of Astartida and Glos- 

 sidcB, but the teeth and form are more like Venerida. 



1. Cyprina, Lamk., Gray, Proc. Zool. Soc. 1847, n. 545. 



Fam. 3. Glauconomid^. 



Shell oblong, covered with a hard green periostraca extending 

 beyond the edge. Hinge-teeth 3 • 3 ; right valve, two anterior 

 small, conical, bent up ; hinder very oblique, elongate, bifid ; 

 left valve, anterior small, middle rather oblique, larger, bifid ; 

 hinder very oblique, small, laminar. Ligament external, mar- 

 ginal ; fulcrum moderate. Lateral teeth none. Siphonal inflec- 

 tion very narrow elongate, ascends obliquely towards the back 

 of the shell, and with a rough muscular scar at the inner end. 



Animal ? 



The Glauconomida difier from the Veneridce in the form and 

 disposition of the teeth, in their freshwater habitation, and in being 

 covered with a hard green periostraca, which, from its external 

 appearance, seems evidently to cover the siphons as in Myada 

 and SolenidcR. 



They differ from Solenida in having more teeth in the hinge, 

 and in the teeth being very differently disposed. 



1. Glauconome, Gray, I. c. n. 549*. The freshwater streams of 

 Asia. 



