456 cardiidjE. 



Californiense, Desk. magnum, Bom. 



ciliatum, Fair. Nuttallii, Conr. 



edule, Linn. ovale, Sow. 



Eicliwaldi, Reeve. setosum, Red/. 



elegantulum, Beck. substriatum, Conr. 



exiguum, Linn. Suecicum, Reeve. 

 Lamarckii, Reeve. 



Sub-gen. serripes, Beck (Aphrodita, Lea. Acardo, Swains.). 



Shell sub-cordate, compressed, rather thin, sub-equilateral; 

 valves with obsolete, radiating ridges, slightly gaping ; beaks 

 rather prominent. Hinge with the cardinal teeth wanting. 



blandum, Gould. modestum, Adams and Reeve. 



Grcenlandicum, Chem. muticum, Reeve. 



Islandicum, Chew. 



Genus papyridea, Swainson. 



Shell thin, smooth, oblong, elongate or transversely oval ; 

 hinder gape moderate, and furnished with a serrated pos- 

 terior margin. 



Ex. P. spinosa, Meuschen, pi. 112, fig. 1, 1, a. 



There are but few species of Payyridea at present known, 

 which are from Madagascar and Australia. 



Species of Papyridea. 



aspera, Sow. spinosa, Meusch. 



hiulca, Reeve. transversa, Sow. 



ringicula. Sow. 



