426 Notes on the Classification of the Corhiculadce, etc. 



The permanent distinctive characters of the genus Corbicula 

 are, that the gills are never soldered behind to that of the 

 opposite side, and that the syphons are always very small. 



I call attention, moreover, to the astonishing affinities exist- 

 ing between Corbicula and Iridina, as far at least as the soft 

 parts are concerned. 



Fig. 7. 



Fig. 8. 



Fig. 7.— The soft parts of Corbicula, the mantle not having been removed, a, the 

 mantle; b, the palleal muscle; c, the anterior adductor; d, the posterior adductor; 

 e, the retractory pedal muscle ; f, the retractory syphonal muscle. 



