RXOTIC UNIONID^fi. 01 



the beaks; cavity of the shell rather deep and wide; cavity of the beaks very small 

 and rounded ; nacre salmon colored and very iridescent. 



Remarks. — This species belongs to the group of which marginalis, Lam., may be 

 considered the type, and to \vli ch Laxjardii, (nobis), and lamellatis, (nobis), belong, a 

 marked character of which is to have a lighter band of color, somewhat yellowish 

 towards the margin, while the remainder of the ep-dermis is more or less brown. 

 Gonsohrinm is, in outline, between Layardii and lamellatis. It is a little stouter than 

 either and has thicker teeth, and the cardinal teeth are shorter and not so lamellar 

 as either of the others. The nacre also is in the specimens before me salmon color, while 

 that in neither of the others is so, they being white. Like both it has the double tooth 

 in the right valve, but in all of them there is a slight disposition to duplication in the 

 left. Owing to the want of perfect beaks, I am unable to say if there be any undu- 

 lations at the tips, but I suspect that very minute ones will be found in perfect 

 specimens. 



