170 MOLLUSCA, 



ft 



that are not typical. They are somewhat narrower, and the whorls 

 are much less convex. They somewhat resemble the specimens of 

 Pleurocera suhulare intensum obtained from Rush Lake. An ex- 

 ample measure's: altitude 17mm., width 7mm., aperture length 7mm., 

 aperture width 4.5mm. 



Amnicolidae. 



89. Amnicola limosa (Say).- — In this region, this species was the 

 most widely distributed of the genus, altho it was the most abundant 

 one only around Caseville. Specimens of Ammcola walkeri were 

 more numerous on Sand Point, and shells of a form of Amnicola lus- 

 trica in Rush Lake. A single juvenile specimen was found on the 

 under-side of a lily-pad in Turtle Bay (8) on Sand Point. Around 

 Caseville it was very abundant in the masses of algae along the Pigeon 

 River (21) and on lily-pads and Potamogeton in the ox-bow pond 

 (22) off from the same. Specimens of this species were quite numerous 

 in Rush Lake, on the under-side of lily-pads in places where the bot- 

 tom was mucky (11) and on the bottom in sandy and gravelly places 

 (14, 15, 16). In these latter places it was found in the very shallow 

 water along the shore. 



90. Amnicola lustrica Pilsbry, var? — Shells referred to this species 

 were found in great abundance off Raymond's, Dune, and Fourth 

 Points (14, 15, 16) at Rush Lake. They differ from typical shells in 

 having the basal whorl larger and more ventricose, and the aperture 

 more nearly circular; these make the shell somewhat broader. An 

 example measures: length 3.90mm., width 2.2mm. 



91. Ammcola walkeri Pilsbry. — ^This species was the most abund- 

 ant- Amnicola on Sand Point, where specimens were quite numerous 

 in a cove on the south side (8) and in one of the more permanent 

 swamps (19). A single juvenile shell was also obtained on the gravel- 

 ly bottom off Fourth Point (16) in Rush Lake. 



92. Amnicola cincinnatiensis Anthony. — Only one specimen of 

 this species was obtained. This was found in a small basin along 

 the shore of the creek portion of Pigeon River (23). It is shghtly 

 smaller than the average, being 4.5mm. in height. 



Valvatidae. 



93. Valvata tricarinata, var. simplex Gould. — Specimens of this 

 form were obtained in large numbers at Rush Lake, off Raymond's 

 and Dune Points (14, 15). They were much more numerous off the 

 latter. Some of the shells approached closely the following form. 



94. Valvata tricarinata, var. unicarinata (De Kay). — ^This shell 

 was collected in large numbers off Dune and Fourth Points (15, 16) 



