I 



UNIO DEHISCENS. 



SPECIFIC CHARACTER. 



Anteriorly biemarginate ; teeth obsolete. 



SYNONYM. 



Unio DEHISCENS. NoMs. Dissemiiiofor of Useful Know 

 ledge, vol. ii, p. 308. 



DESCRIPTION, 



Transversely much elongated, thin, rather compressed 

 polished, pale yellowish green, or hrownish, radiate 

 with somewhat interrupted green lines which are more 

 or less dilated and compound, and obsolete in the aged 

 specimen ; anteriorly gaping, and at the posterior inferior 

 margin also gaping nearly to the middle of the base; a 

 slightly impressed line on the anterior hinge submargin 

 passes to tlie anterior margin, which is emarginate both 

 above and below the line, and subangulated at tip : posie- 

 rior margin rounded, extending considerably beyond the 

 beaks : \imho and heak not prominent, with slight undula- 

 tions on the latter : primary teeth consisting of a slightly 

 elevated, very obtuse angle in the right valve and obsolete 

 sinus in the left for its reception : lateral teeth denoted by 

 an impressed line; cavil ij of the tnnbo sVight, but with a 

 deep, obvious and large muscular impression, immediately^ 

 under the beak ; more or less tinged with purple- 



