﻿366 ANODONTA 



species could have fallen into the hands of the new school of 

 conchologists in anv such ahundance as has the unfortunate 

 Anodonta cygnca, we would have had several genera and many 

 thousands oi species erected on their ruins. 



I have endeavored to recognize a few of the more striking 

 forms as varieties, and I have referred them to the author 

 originally descrihing them and to a few well-known references, 

 hut I have not heen ahle to work out at all thoroughly the very 

 elahorate synonymy for these variations. 



The species in general mav he known hv its exactly or al- 

 most exactlv rounded anterior end. hv its moderate wing, the 

 often incurved post-dorsal truncation, hv usuallv heing feebly 

 hiangulate behind and ending in a point or biangulation at 

 some distance above the base, and hv its normallv compressed 

 beaks, sculptured over a wide area with rather fine, concentric 

 or slightly wavy bars. 



Anodonta cygnea Linnseus. typical. 



According to Hanley (Shells of Linnaeus, p. 144) the A. 

 cygnca var. ccllcnsis of Rossmassler (Icon.. l\ , 1830. ])1. xix, 

 fig. 280) is marked for this in the Linn?ean cabinet. Tt is a 

 large, rather elongated shell, slightly biangulate behind, some- 

 what cut away on the upper posterior part. 



The wing behind is not sharply angulated, the posterior ter- 

 mination is about midway up from the base, the surface is 

 sculptured, especially the later growth, with low, irregular, 

 concentric ridges, the color is ashy, often banded with straw, 

 bufif. green or brownish and generally rayless. 



Tvength t8o. height 80. diam. 50 mm. 



\'ar. anatina (Linn?eus). 



v^hell rather small, com])ressed. narrowed and rounded in 

 front, with a low dorsal wing which is not much angulated at 

 the junction with the posterior slope; posterior termination 

 rather sharp, elevated but little above the base; surface ray- 

 less, ashy or yellowish-green, often with darker concentric 

 bands. 



Length 80. height 42. diam. 18 mm. 



