80 AN ANNOTATED CATALOGUE 



space of a few yards. A notable instance of this kind was 

 noted ill the Des Moines river, a few miles north of Des 

 Moines. The situation was at the lower extremity of an 

 extensive sandbar, where the water during the summer is 

 usually from three to five feet deep, and with little or no 

 current ; notwithstanding the close proximity of the sand- 

 bar, the bed of the stream is muddy. Here thousands of 

 mussels lie buried in the mud, so closely as nearly to 

 touch one another. Every haul of the rake — a large gar- 

 den rake, very suitable and serviceable in collecting of this 

 kind — affords a half dozen or more specimens, and in a 

 very short time a bushel or more of Uniones have been 

 obtained. The species represented in order of their relative 

 abundance, are : Unio ligamentinus, U. luieolus, U. ven- 

 tricosus, U. pustulosus^ M. complanata^ U. undulatus^ 

 A. grandis, U. rubiginosus, U. gibbosus, besides eight or 

 ten other species in fewer numbers, and Campeloma sub- 

 solidum in profusion. 



Unio lunulatus Pratt. This form is described in the 

 Proceedings of the Davenport Academy of Sciences, 

 volume I, from specimens collected in the Mississippi 

 at Davenport. It is very closely allied to Unio lach- 

 rymosus Lea, with which according to Call it is perhaps 

 synonymous. 



Unio luteolus Lamarck. Everywhere abundant. A 

 variety having a remarkably thin and fragile shell, which 

 externally is scarcely distinguishable from an Anodonta 

 associated with it, is found in abundance in Lake Minne- 

 tonka, Minnesota. 



Unio metanever Rafinesque. Abundant in the streams 

 of eastern Iowa, but in the central part of the state 

 it is replaced by a lighter colored and more compressed 

 variety, U. wardii Lea, the latter being very rare in the 

 eastern portion of the state. 



