﻿LAMPSILIS 65 



epidermis slightly wrinkled, straw-color or greenish-yellow. 

 Left valve with two small i>seudocardinals and two somewhat 

 remote laterals, the former just in front of the beak ; right 

 valve with two pseudocardinals, the upper one smaller and 

 compressed, and a single, high, truncated lateral ; beak cavities 

 shallow; anterior muscle scars rather deep, posterior scars 

 semicircular ; nacre bluish-white, dull, often with a lurid blotch 

 in the cavity of the shell. 



Length 58, height 34, diam. 20 mm-. 

 Upper Great Lakes region. 



Type locality, Michipicoten River, north shore of Lake Su- 

 perior. 

 Unio snperiorcnsis Marsh, Naut. X, 1897, p. 103, pi. i, figs. 



I, 2, 5. 

 l.ampsilis superiorensis Simpson, Syn., 1900, p. 535. 



Close to Lmnpsilis lutcola and possibly a variety of it. This 

 and /.. horcaUs form connecting links between L. hiteola and 

 L. radiata. though they appear to be as well worthy of spe- 

 cific rank as a large number of our forms. The present species 

 is smaller and rather more compressed than the L. lutcola, the 

 texture of the shell is different ; it is not so bright and shining 

 as that species and it has a duller nacre. 



Lampsius borkalis (A. F. Gray). 



Shell solid, inflated, long obovate, sometimes having a slight 

 posterior ridge ; beaks rather full but not high ; epidermis hav- 

 ing fine, concentric folds, often wrinkled in front, scarcely 

 shining ; surface with few to many rather feeble, dark greenish 

 rays on a greenish-brown or brown ground; left valve with 

 two stumpy pseudocardinals, the hinder under or a very little 

 forward of the beak, and two rather remote, straight laterals ; 

 right valve with one strong, roughened pseudocardinal, a 

 small, compressed one above it, and one high, subtruncated 

 lateral ; beak cavities rather deep and wide, with a few im- 

 pressed dorsal pits ; anterior scars smooth, deep ; posterior scars 

 faint ; nacre whitish or bluish-white, dull, often having lurid 

 blotches. The male shell is more elongated, more pointed be- 

 iiind than the female, which has a slight swelling just behind 



