THE NAUTILUS. 125 



rounded angle situated rather inferior. Surface with irregular, 

 rather fine stride, slightly shining; color of epicouch pale or grayish 

 horn ; shell moderately thick ; nacre whitish-glassy ; hinge rather 

 stout; cardinal teeth lamellar, the right moderately curved, not 

 reaching the inferior edge of the hinge plate, with a rather deep 

 groove below ; the left anterior cardinal tooth moderately or rather 

 strongly curved, the posterior oblique, moderately curved, with a 

 deep groove between them ; lateral teeth rather strong, finely crenu- 

 lated or rugulose, those of the left valve strongly, those of the right 

 valve slightly projecting over the valve edge, and the latter also 

 into the cavity of the mussel ; ligament strong. 



Size : long. 4 - 2 i'7, alt. 2'5-3'0, diain. 2 - 5-3 mill. 



Habitat. The species has a wide geographical distribution ; 

 Michigan, many places in the Upper and Lower Peninsula ; south- 

 ern Minnesota; Pedan River, Canada; Philadelphia, Pa.; Adams- 

 ville, N. J. ; Couial Co., Texas. 



It is surprising that such a well characterized Pisidium has not 

 been noticed before this. Careful comparison with the earlier de- 

 scriptions of T. Prime shows that it cannot be identical with any of 

 those species. 



Pis. trapezoideuni is somewhat variable in size and shape ; the 

 angles at the scutum and scutellum are more rounded in some forms, 



o 



and so the superior margin is more curved, the beaks are more or 

 less flattened on top, sometimes almost imperceptibly. 

 New Philadelphia, Ohio, February, 1896. 

 (To be Continued.') 



ANNOTATED LIST OF THE MOLLUSCA FOUND IN THE VICINITY OF 

 CLEARWATER, WRIGHT CO., MINNESOTA. 



BY H. E. SARGENT, WOODVILLE, ALA. 



Part Kecond Aquatic Species. 



In searching for aquatic specimens a ten quart tin pail and a wire 

 gauze dip net were the implements made use of. Sediment and 

 specimens were dipped into the pail and washed by repeated stirring 

 and decantation. By this means the most minute specimens were 

 retained for future sifting and sorting. 



