16 



SYNOPSIS OF 



r f 



m 

 a 



o 



t> 

 a 



H 



o , 

 as 



t- 

 cc 



s 



z 



o 

 z 



SUBROTUND. 



*dromas. Lea. 



OBLIQUE. 



*.^sopus. Green. 

 Unio cicatricosus. 

 Unio varicosus. 



Con. ; not of Say. 

 Con. ; not of Lea. 



* varicosus. Lea. 



Unio cicatricosus? Say.] 



*perplexus. Lea. 



Unio gibbosus? Raf. 

 Unio gibbosus. Con. 



WIDE. 



*Leaii. Gray. 

 *granosus. Brug. Lam. 

 *tuberculatus. Bar. Eat. Hild. 

 Novae Hollandise. Gray. 



II 



*cylindricus. Say. 

 Unio naviformis. 



Eat. Hild. 

 Lam. Blain. Valen. 



B fwiDE. 



2 ) *spinosus. 



Lea. 



02 



w 

 z; 

 o 



z 



H 

 O 



5^ 



a 



m 



Z 

 O 

 Z 



QUADRATE. 



*arc8eformis. Lea. 

 Unio nexus. I iSa?/. 



TRIANGULAR. 



*triangularis. Bar. Eat. Hild. Say. 

 Unio formosus.§ Lea. (Male.) 

 Unio cuneatus. Swain. 



*elegans.|| Lea. 

 *donaciformis.Ty Lea. 

 *zigzag. Lea. Eat. 

 *beterodon. Lea. 



^penitus.jf Con. 



'^securis. Lea. Eat. 

 Unio depressa.|| 

 Lam. 



Raf. ; but not of 



t Never having seen the specimen described by Mr Say as cicatricosus, I am unable to decide if it be the 

 same vi^ith varicosus (nobis). Two things mentioned by Mr Say induce me to doubt it. He calls his " a com- 

 mon species," and says it is " distinguishable by the single series of transverse elevations on the middle." The 

 latter remark does not apply to varicosus, and I have always deemed it a rare shell. 



X Say and Conrad both commit the error of giving precedence to nexus. My description of arcaeformis is 

 in my memoir, read before the American Philosophical Society May 30, 1831, while Mr Say's was first de- 

 scribed in the Transylvania Journal of December 1831. Subsequently he republished it in his American Conch- 

 ology, No. 6, where he places erroneously the date of 1832 to my memoir. 



§ Mr Barnes's description of triangularis was made from a female shell, and mine oi forma sus from the 

 male. There being an obvious distinction of the sexes in every specimen, my error was a very natural one, as 

 we were not at the time acquainted with the sexual differences in the Naiades. 



II Mr Say thinks that Mr Barnes's undulatus, Var. a, is the same with elegans. I think differently, and 

 would fortify my opinion in the fact, that Mr B. does not mention the zigzag rays which are strikingly singular 

 in the elegans, and could not have failed to have elicited his remarks had it been under his eyes. 



f I have expressed my doubts, Transactions of the American Philosophical Society, Vol. IV., page 84, (page 

 94 in " Observations on the Genus Unio," &c.,) if this be more than a fine variety of zJ^ra^ (nobis). Mr Say 

 gives it as a synonym to nervosvs, Raf, and Mr Conrad as truncata, Raf. 



tt I received from Judge Tail of Alabama, in 1830, several specimens of this species, but they were not 

 sufficiently perfect to induce me to publish them. Mr Conrad does not mention the rays, a very peculiar cha- 

 racter of which is their being dotted somewhat like those of securis (nobis), but in a lighter manner. 



tt Mr Conrad makes dcpressa, Raf., eUipsaria, Raf., and securis (nobis), synonymous with lineolutu. 



