MOLLUSCA. 169 



84. Physa elliptica Lea. — This shell appeared to he quite rare in 

 the region studied. A few specimens were found in a temporary 

 swamp (18) and in a perennial swamp (19) on Sand Point, and in the 

 dead waters of the Pigeon River (24). An example measures: alti- 

 tude 7.5mm., width 4.5mm., aperture length 5.5mm., aperture width 

 2mm. 



85. Physa Integra Haldeman.— A few juvenile shells of this species 

 were collected among algae, principally Vaucheria, in the creek and 

 river portions, and on the under-side of Hly-pads in the dead water 

 of the Pigeon River (23, 21, 24). 



86. Aplexa hypnorum (Linne). — ^This shell was very abundant in 

 the temporary swamps (18) on Sand Point, Stony and North Islands, 

 and around Rush Lake. Juvenile specimens were also obtained from 

 a perennial swamp (19) on Sand Point and from one near Rush Lake. 

 The shells are quite narrow: a representative specimen from Sand 

 Point measures: length 14.25mm., width 6mm.; from Stony Island: 

 length 15mm., width 6.25mm.; from Rush Lake: length 17.5mm., 

 width 7.5mm. 



PECTINIBRANCHIA. 



Pleuroceridae. 



87. Pleurocera subulate, var. intensum (Reeve). — This species 

 was found in great abundance off Raymond's Point (14) in Rush Lake, 

 living in from about six to forty-eight inches of water. An example 

 measures: altitude 21.5mm., width 8mm., aperture length 7.5mm., 

 aperture width 4.5mm. 



88. Goniobasis livescens (Menke).^ — ^This species was found in 

 great numbers in the unprotected, rocky, littoral habitats off the north 

 shores of both North and Stony Islands, both on the Hmestone rock 

 that forms the bottom and on piers of wharves, etc., in the same 

 localities (2). It was also collected in rock pools (3) along these 

 shores. In the Pigeon River (21), from about one-half mile from the 

 mouth up as far as the creek portion, these molluscs almost cover the 

 stones on the bottom. A single specimen was found on Potamogeton 

 in the ox-bow pond (22) off from this river. A few specimens were 

 also found on the rock bottom off Little Oak Point (2). 



The shells obtained off the shores of North and Stony Islands and 

 Little Oak Point are heavy, and often have concretions of marl on 

 them. Those from the Pigeon River are comparatively fragile, 

 strongly malleated, and encrusted with a growth of algae. 



Goniobasis livescens, var. — A few shells were obtained off Sand 

 Point in deep water (1) and one from shallow water off Twin Bars (5) 



