23 



(SUBROTUND. 



*dromas. Lea. 

 *Lamarckianus. Lea. 



OBLIQUE. 



; , *.ZEsopus. Green. 



Unio cicatricosus. Con. 



Unio varicosus. Con.; not of Lea. 



Unio cyphius. Con. 



*varicosus. Lea. Chenu. 

 Unio cicatricosus? Say. 1 

 Unio cicatricosus. Con. 



*perplexus. Lea. Kirtl. Chenu. 

 Unio gibbosus? Raf. 

 Unio gibbosus. Con. Kust. (Fig. 3.)' 



WIDE. 



*Leaii. Gray. Benson. 3 



granosus. Brug. Lam. 



*tuberculatus. Bar. Bat. Hild. 

 Unio pustulata. Sivain. 



2 -! 



fWIDE. 



Novae Hollandiae. Cray. 



*cylindricus. Say. Eat. Hild. 

 Swain. 

 Unio naviformis. Lam. Blain. 

 Valen. Desk.* 



TRIANGULAR. 



*spinosus. Lea. Chenu. 

 *collinus. Con. 



-QUADRATE. 



*arc£eformis. Lea. Besh. Chenu. 



Unio nexus. 5 Say. 



TRIANGULAR. 



triangularis. Bar. Bat. Hild. Say. 

 Unio formosus. 6 Lea. (Male.) Chenu. 

 Unio cuneatus. Swain. 



*Foremanianus. Lea. Chenu. 



*elegans. 7 Lea. Chenu. 

 Unio truncatus. Say. 



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

 with varicosus (nobis). Two things mentioned by Mr. Say induce me to doubt it. He calls his "a common species," 

 and says it is "distinguishable by the single series of transverse elevations on the middle." These remarks do not 

 apply to varicosus, but they do to JEsopus, Green, and I have always deemed it a rare shell. 



2 Kuster figures (3) a male perplexus (nobis) as gibbosus, Raf. His figure 4, also called gibbosus, is a female 

 Rangianus (nobis). 



3 Dr. Cantor, in the Annals of Nat. Hist., vol. 9, p. 489, gives the habitat of this species in Chusan and in 

 Canton River. He also describes a Unio, under the name of divergens, being "tuberculato-plicata;" also, an Anodonta 

 (gibbum), both from Chusan. 



4 Deshayes, in Encly. Meth. Vers., torn. ii. p. 580, No. 5. 



5 Say and Conrad both commit the error of giving precedence to nexus. My description of arcseformis is in 

 my memoir, read before the American Philosophical Society, May 20, 1831, while Mr. Say's was first described in 

 the Transylvania Journal, of December, 1831. Subsequently, he republished it in his American Conclwlogy, No. 

 6, where he places erroneously the date of 1832 to my memoir. 



6 Mr. Barnes's description of triangularis was made from a female shell, and mine of formosus 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. 



7 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 elicit his remarks had it been under his eyes. 



