OF THE FAM1M ui N \l \!>! - ||, 



AUumod&nta of Say. have been mentioned by two eminenl 

 English eonchologists, W. Swainson and (i. B. Sowerby, a- 

 well as in America by P. II. Nicklin. Mr Sowerby (Zool. 

 Journ. Vol. I. p. 55.) lias reunited them under the name oi 

 Efato, of which he makes two greal divisions: L. ^W it li< »n t 

 teeth. 1. With teeth; and these are each subdivided into 

 "winged" and -not winged:" which are again divided into 

 the various forms of teeth, or the -hinge line." The evident 

 objection to this arrangement is the difficult] of deciding 

 upon the passage from the "no! winged" to the "winged." 

 Thus we do no1 find the Jbnodtmta trapezialis and .inodon/n 

 glauca, which Lamarck describes as " compresso-alatd" men- 

 tioned among the -winged." while we have ■• . bwdon alahu 

 of Swainson and Lamarck." which is not described in the 

 "Hist. Nat. des Animaux sans Yertebrcs*." 



It is evident that the apparatus for depositing the calca- 

 reous and epidermal matter on the elevated and connected 

 wing musl be different from that of the inhabitant of free 

 valves, to which it has been denied by nature. 



Lamarck and Barnes both mention in their description oi 

 the U. aktfou of Say. that M. Le Sueur thoughl this shell 

 should constitute a new genus. Since that time so man} 

 connate shells bavecome to my notice, that I feel satisfied the 

 science of conchology will be subserved by the institution oi 

 this natural genus, which will embrace, in all probability, 

 several others, viz. Hyria of Lamarck, /Jipstts of Leach, and 

 Cristaria, Prisddon, ami Paxyodon of Schumacher, all of 

 which, when they shall he found perfect, will most probabl] 

 turn out to be connate shells. Lamarck suspected Ins Hyria 

 to be connate, like the U. alahu; for when describing that spe,- 



-. he says, •• \os Hyriea auraient-elles one pareille reunion 



moat be considered ecieaof Unio, and not a genua. Theob- 



ii' M. De BlainviUe has placed CattaMa and Hyria among the Uidonct, and 



Tridina and Dipsat among the Anadonta. Ca Udia ambigua u undoubtedly a 



moat cloiely to the V. triangularig. The -«-«-c !• 

 "iili'- Unio, and il differs only in iti longitudinal furrows from I i 

 ral char m - I oio. 



icribea Ms An. gibbo ta i- beii 

 vol. nr. — ; ' 



