uisrio. 



39 



r TEIANGULAR. 



Unio mytiloides. 

 Unio undulatus. 

 Unio cordatus? 

 Unio cordatus. 

 Unio caridiacea. 



Sh. d- Eat. 



Desk. 

 Raf. 

 Con. Kilst. 



Ouerin. 



Mya undata. Eat. 



*23lenus. Lea. 



*pyraniidatus. Lea. Kilst. Chenu. 

 Desh. Han. 

 Unio rubra'? Raf. 

 Unio mytiloides. Con. 

 Unio cardiacea. Desh. 



*Bournianus. Lea. Chenu. 



*Edgarianus. Lea. Chenu. 



*Mooresianus. Lea. 



*mytiloides.^ Raf. Sivain ; not of 

 Desh. 

 Unio triangularis. Con. 

 Unio rubra. Con. 

 Unio caridiacea. Con. 

 Mya obliqua. Wood. 



TRIANGULAE. 



Unioj^sis mytiloides. Swain. 



OBLIQUE. 



*Troostii. Lea. Han. 

 Unio trabalis. Con. 



^tross^ilus. Lea. 



lepidus. Gould. 



*Tigris. Fer. 



Unio Tiyridis. Bourg. 



*Pazii. Lea. 



*terminalis.^ Bourg. Mouss. Trist. 

 *tumidulus. Lea. 



cor. Con. Han. 



truncatus. Sivain. Han. 

 ^Bourgnignatianus. Lea. 

 *dignatus. Lea. 



1 It is a matter of great doubt if this name ought to be admitted at all in this table. It was applied, 

 manj^ years since, by the naturalists of this city, without reference to any particular specimen, but, as it 

 now appears nearly certain, incorrectly. Dr. Ward says the description and outline would " equally well 

 apply to sis or eight different species." The difficulty of recognizing Mr. Kafluesque's species is well 

 illustrated in this one. Mr. Conrad, in New Fresh Water Shells U. S., considers triangularis, Raf., as 

 the type, and gives the following names of the same author as synonyms, viz., lateralis., sinioxia, 

 pachostea, mytiloides, and rubra; thus charging him with making six species of one. But, what is still 

 more extraordinary, this single species (agreeably to Mr. Conrad's synonyms) is not only divided by 

 Mr. R. into different subgenera, but into different genera, and even into two different sub-families ! ! 

 See New Fresh Water Shells of the United States, p. 72, and Mr. Raflnesque's Monographie. In Mr. Say's 

 Sijnonymy, triangularis, Raf., is considered to be the same as ellipsis (nobis) ! Deshayes described a 

 different shell under the name of mytiloides. {Ency. Meth., p. 249, Pig. 4.) I doubt from this figure if it 

 be not a complanatus. We certainly have in our rivers, occasionally, specimens of this protean species 

 very closely resembling this figure. M. Desha3^es's figure has some resemblance to an imperfect 

 Batavus. The habitat is not known. The confusion is increased by Mr. Conrad's subsequent attempt 

 at correction. In Monogra2:>hy, 1836, he makes mytiloides a type, and puts rubra, Raf., p>yramidatus, Lea, 

 and caridiacea, Gu^rin, as synonyms. Subsequently, in Synopsis of 1853, mytiloides and triangularis 

 are both dismissed as tj^pes, and the former made synonym to clava, Lam., while the latter is made 

 synonj'm to triqueter, Raf.!! 



^ Mr. Tristam, in Proc. Zool. Soc. 1865, p. 543, says he thinks that terminalis and Jordanicus, Bourg. 

 are the same, and that dignatus (nobis) seems to him to be identical with terminalis, but I doubt it. 



