xjisrio. 



43 



f OVAL. 



*flavesceiis.' Lea. 



*pictus. Lea. Han. 



*fucatus. Lea. 



*pallescens. Lea. 



*perpastiis. Lea. 



Mortonicus. Reeve. 



^Tennesseensis. Lea. Chenii. 



""intemiptus. Lea. Chenu. Han. 

 Unio t^niatiis. Con. Han, 

 TJnio latiradiatus. Con. 



*Menkianus.' Lea. Chenu. Han. 



*bracteatus. Gould. 



*Lmdsleyi. Lea. 



^piinctatus. Lea. 



*Stonensis. Lea, 



*veniistus. Lea. Chenu. 



■"exiguiis. Lea. Chenu. Han. 



OVAL. 



*Eutersvillensis. Lea. 



*Topekaensis. Lea. 



*planicostatiis. Lea. 



*spatulatus. Lea. 



*Ant]ionyi. Lea. 



*ligamentiiius. Lam? Kust. 



Unio a-assus. Say. Bar.^ Hild. 



Kirtl. Han. 

 Unio ellipticus. Bar. Hild. 

 Unio carinatus. Bar. 

 Mya elliptica. Eat. 

 Mya carinata. Bat. 

 3Iya crassa. Bat. 

 Mya gravis. Wood. 

 Unio fasciatus. Con.^ Kust, 



*exactus. Lea. 



*purus. Lea. 



*cognatus. Lea. 



^Plantii. Lea. 



*orbiculatus. Hild. Kirtl. Han. 

 Unio alruptus.^ Say. Desh. 

 Unio crassus. Con. 



1 This may be a variety of Greenii, Lea. 



2 Koch and Dunker described a fossil species (Menliei) in 183T: Beitrdge zur Kenntniss, p. 58. My 

 species was described in the Trans. Am. Phil. Soc. 1836, and must therefore have precedence. 



^ Having recently had access to Retzius's work (1T88), I find that he described a European Unio 

 under the name of crassus, which species had been admitted into our systems under the name of crassis- 

 simus, Fer., I now restore it to its proper place under the name of crassus. Mr. Say described his crassus 

 as having "waves;" but his figure, inside view only, certainly is a species without "waves." 



Deshayes thinks that U. ligamentinus is analogous to U. muUiradiatus, and probablj^ a young indi- 

 vidual of it. This is not likely to be the case, however. The species are very different. 



* Mr. Barnes made eleven varieties of crassus; most of which were, no doubt, distinct species; some 

 were plicate. 



^ Mr. Conrad thinks the crassus of Say is fasciata of Eafinesque. An examination of his description 

 ought to satisfy any one that the crassus of Say could not have been under the eye of the author when 

 he made his description ot fasciata. 



« The specimen figured by Say, in Ame?: Conch. No. 2, is a female shell. The male shell is not abrupt 

 at the posterior margin. 



