THE NAUTILUS. 125 
rounded angle situated rather inferior. Surface with irregular, 
rather fine striz, slightly shining; color of epiconch 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. 4:2-4:7, alt. 2°5-3-0, diam. 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.; Comal 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. trapezoideum is somewhat variable in size and shape; the 
angles at the scutum and scutellum are more rounded in some forms, 
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 Second—Aquatie 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. 
