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FOURTH SUB-FAMILY Alasmidia. 



Shell transverse ; one primary anterior tooth ; 

 no lamellar tooth. 



Tenth Genus ALASMIDONTA. 



Shell oval or elliptical, axis extramedial ; three 

 cicatrices or muscular impressions ; ligament 

 straight, imbricated, &c. 



SPECIES LX. Alasmidonta marginata. 



Shell oval-elliptical ; sloped posteriorly, with 

 oblique, obtuse wrinkles ; epidermis olive brown, 

 radiated with green, and wrinkled zonally ; nacre 

 bluish white, with white edges; tooth simple, 

 compressed, oblique. Length J of the breadth. 



This genus and species were established by 

 SAY ; (vide Journal of the Academy of Natural 

 Sciences of Philadelphia, vol. i. p. 459,) who 

 also refers to this genus the Unio undulatus (vide 

 American edition of Nicholson's Dictionary, ar- 

 ticle Conchology and Tab. III. fig. 3.) ; to these 

 must be added also the following species. 



The above described species is found in the 

 Scioto river ; length two and an half inches. J 



