REFERENCE TO THE PLATE. 



Interior, exterior and 'ioreal views. 

 PI. 53. 



UNIO QUADRULUS. 



SPECIFIC CHARACTER. 



Shell siibquadrate, tuberculated, with a nodulous ridga 



aad dilated groove. 



SYNONYMS. 



U. quADiiuLUS, Ii(ff.. Jinn. gtn. dcs Sc. Phys, vol. 5. 



IT. RUGosus, Barnes^ Sillimans Journ^ vol. 6, p. 126. 



Hildrcth SHlinimts Journ. vol. 14, p. 2S2. 

 U. LACRYMOsus, ? Trcms. ^flmcr. Philos. Soc. N. S. vol. 



U. ASPERRIMUS, 5 ^ ^"tl 4. 



DESCRIPTION. 



57ic// narrowed, compressed and thin before ; short, ob- 

 tuse, rounded and wider behind ; beaks slightly elevated : 

 ligament more elevated than the beaks : liinge inar^iti 

 compressed, carinate ; basal 7nargin falcate, emarginate, 

 and compressed : anterior margin subangulatc : anterior 

 dorsal margin subtruncate, nearly straight : anterior ba- 

 sal margin projecting : epidermis dark brown, under the 



PI. 53. 



