306 WEST COAST SHELLS 



sand and grit. Lifting the net out, I was surprised 

 to find a common Eastern Musculium, M. partu- 

 meium^ Say, PI. i, Fig. ^, among the spoils. This 

 was a lind and I gathered many specimens, dumping 

 them into a tobacco-tin along with grit, etc., to be 

 sorted out on my return, when dry. 



This species appears to be an old settler for it has 

 turned up since at a number of places on the coast. 

 The shape is nearly circular, except it is squared off 

 posteriorly. It is not generally very inflated and 

 the umbos are low. Found in pools and lakes prob- 

 ably all over northern and central United States 

 and southern Canada. 



Raymond's Calycule shell, Musculium raymondi^ 

 J. G. Cooper, PL I, Fig. 3, differs from the preced- 

 mg by its trigonal shape and high inflated umbos. 

 Its habits are similar and it is found in the Colum- 

 bia, Klamath, Nevada and Coast Range Systems. 

 Its identity has been suggested with M. rlivkolti^ a 

 P^uropean species which is said also to occur in the 

 Eastern States. 



Pisidium ahditum^ Haldeman, the Hidden Pea- 

 shell, Plate I, Fig. 1, is a tiny fellow found in 

 springs, quiet streams, and ponds all over North 

 America. Like most widely distributed species it 

 is rather variable and has been given a number of 

 names. It is rather small for the genus, ovate, 

 rather inflated, with low nearly central umbos, and 

 it is usually brown in color. 



Pisidium co7?ipressu?n. Prime, the Trigonal Pea- 

 shell, PL I, Fig. 2, differs in being very inflated and 

 trigonal, with high umbos. It is yellow or brown 



