﻿DESCRIPTIVE 

 CATALOGUE OF THE NAIADES 



I. 



Family UNIONID^. 



Shell nacreous, with a thick epidermis ; beaks usually sculp- 

 tured, often showing the remains of the nuclear shell ; ligament 

 opisthodetic ; hinge with or without teeth, though with vestiges 

 of them in every genus ; when present schizodont and arranged 

 as pseudocardinals and laterals ; pallial line usually simple ; 

 prismatic border ordinarily narrow. 



Animal with labial palpi almost always wider than long; 

 anal opening usually separated from the superanal ; embryo a 

 glochidium, the soft parts being inclosed in a bivalve shell and 

 borne in the inner or outer or all four leaves of the branchiai. 



Subfamily UNIONIN/E Swainson, 1840. 

 (Kxobranciii.^.) 



Shell having essentially concentric beak sculpture. 

 Animal with labial palpi somewhat drawn out, projecting 

 posteriorly ; embryos borne in the outer or in all four gills. 



HETEROGEN.^. 



Male and female shells different, the latter inflated in the 

 post-basal region ; beak sculpture decidedly doubly looped ; 

 embryos contained in ovisacs separated by a sulcus and occu- 

 pying the hinder part of the outer gills. 



