266 [liEBKUAKX, 



very distinct species, the prasinus being much longer comparatively, with 

 fewer and less-prominent tubercles, and arranged in a very different manner. 

 The cardinal plate under the beaks is not dilated ; in the nodulatus^ it is pro- 

 f Hindi y dilated, a very important difference, which it is strange should have 

 b -en overlooked. Young shells of prasimis and bidlatus, when compared, are 

 strikingly dissimilar. 



(/.) U. purpurattis, Lam. There is no doubt that Solander named this species 

 ventricosa, as Humphreys terms it " La Ventrue rouge," and gives the habitat 

 of "Mississippi river," where it abounds, and where no other species has beer 

 found which agrees with the description. 



(7.) Z7. qicadndus is not 11. rugosus, Barnes. Mr. Lea remarks that some of 

 our best Western conchologists think Z7. mgosus identical with 77. fragosus. 

 Barnes' figure certainly has little resemblance to the latter, and the " broad 

 nodulous, somewhat dotible ridge," wholly inapplicable to quadmlus. Mr. Lea 

 says, *' two specimens referred to by Mr. B. as rugosus, were under my inspec- 

 tion, and proved to be, the one a flat metaiievery and the other a plicatus.^^ Now 

 the rugosus may be the metaiieurus , Raf., but Barnes' figure was never intended 

 for any variety of the TJ. plicatics, 



Mr. Say has unfortunately copied Barnes' description of Z7. rugosus , and 

 applied it to U. quadrulus, Raf. 



(.) JJ. undatus. It has been supposed that this was the shell described by 

 Mr. Lea as trigonus^ but it is distinct. There is a fine specimen of tmdatus in 

 the collection of the Academy, which agrees perfectly with Barnes' figure, and 

 is much more ventricose anteriorly and over the umbo, than trigomis ; has more 

 elevated beaks, and is very inequilateral, whilst the latter is nearly equila- 

 teral. The uiidatics is equallyj^distinct from cordatus, Raf., which is compara- 

 tively compressed. 



Compare Barnes* description, " subtriangular, very tumid, waved," with La- 

 marck's description of U, obliqua, *' ovato-rofundate, oblique," and the discre- 

 pancy must strike every one ; yet both Lea and Deshayes make them one 

 species. 



Z7. tcndulat2is, Barnes. The old specimens of this species have so much 

 resemblance to Say's heros, as even to have deceived Say himself, who aban- 

 doned his species, and referred it to Barnes's undulaUis ; but it is a very 

 distinct species, the young shell having little resemblance to that of the latter. 

 There can be no doubt that Barnes figured the species now known as the 

 eostatus of Raf. 



(o.) U. viridis, Raf. Mr. Lea gives another name to this shell, because he 

 says it is not Rafinesque's species, which it certainly is ; yet he does not 

 acknowledge Rafinesque as authority, for he applies his specific names, as in 

 the case of Z7. interruptus, to a species of his own ; consequently the shell in 

 question should have been quoted by him as TJ. viridis. Con., unless he has one 

 rule applicable to himself and another referable to other authors. The shell 

 labelled viridis by Rafinesque himself in Mr. Poulson's cabinet, is the same as 

 Lea's Tappianus. 



Anodonta. 



(a.) A. cataractay Say. The Mytilus jiicviatilis of Gmel. and Dillwyn, and 

 the M. illitus of Solander, appear to be merely names given to the JJnio ochra- 

 ceus in Lister's work, t. 157, fig. 12. The two AuodoiUa.'i figured by Lister, t. 

 154, 155, and having Virg. inscribed upon the plates, I cannot refer to any of 

 our species. 



(5.) A. marginata^ Say. Dekay regarded this shell as the young oi implicatay 

 and it is not unlikely his opinion was correct. It certainly is not Say's 

 eataracta. 



