'3. U. ovatus, 



4. U. cariosus, 



5. U. nasutus, Say, 



6. U. cylindricus, Say, 



7. U. subtentus, Say. 



OF THE FAMILY OF NAIADES. 



Say*' J ovata, 



riuteola, 

 I cariosa, 

 •^ crassus (old)f, 



carinatus (rayed), 

 l^ellipticus (young), 



rostrata, 



naviformis. 



Sayt, 



( navi 

 I navi 



formis, 



' crassidens "? 

 peruvianas, 

 rariplicata, 



8. U. plicatus, Le Sueur§, -^ undulatus, 



crassus, 

 undulata, 

 dombeyana. 



417 



Lam. 

 Valenciennes. 



Lam. 



Lam. 



Say. 



Bar. 



Bar. 



Valen. 



Lam. 

 Valen. 



Lam. 



Lam. 



Lam. 



Bar. 



Bar. 



Valen. 



Valen. 



therefore, with the rules of nomenclature, I have inserted the name of complana- 

 tus to the shell described by Mr Say under the name of purpureus. 



* Dr Hildreth, in describing this species of Say, says, " I think it a near rela- 

 tion of the gracilis ;" and, when describing the gracilis, he says, " The contour 

 of the shell, independent of the wing, is much like that of the alatus." In the lat- 

 ter he is right, but in the former remark altogether wrong. 



Donovan, Dillwyn, Maton and Racket, and some other British writers have 

 made use of this name for a Unio resembling the pictorum. I have thought it bet- 

 ter, however, to retain Mr Say's name for his species, which is totally different, 

 being satisfied that the Britisli shell is only a variety of^ ■pictorum. 



t This is probably the only species yet known to be common both to the Wes- 

 tern and Atlantic waters. 



I Crassus is omitted in this catalogue, believing that several other species, and 

 those only because they were ponderous, have been described under this name. 

 Mr Say's crassus (See Am. Conch, plate 1, fig. 8,) is evidently an old and ponde- 

 rous cariosus, and he considered the ^'■plicatus" as a variety. Mr Barnes's cras- 

 sus is an old and thick pcruvianus, as is most likely Lamarck's crassidcns. The 

 giganteus of Dr MitchiU's collection is also a peruviamis, which occurs in some of 

 our western waters of a larger size and more ponderous than any species we 

 know of. 



§ This species was first described by Say in the American Concliology as a va- 



