THE MOLLUSC A OF GEORGIAN BAY 103 



SESSIONAL PAPER No. 39b 



Genus Ancylus. 



Ancylus is represented by a single species. 



Ancylus parallelus, Hald.; very common in sheltered bays on under sides of 

 lily leaves and on sticks. Shell flat, pyramidal; apex ^ length of shell from posterior 

 end, directed backwards and to the left; sides nearly parallel, shell narrower in 

 front. (PI. XI, Fig. 17). 



Family streptomatidae. 



Represented by two (?) species of the Genus Goniobasis. 



Genus Goniobasis. 



Goniobasis livescens, Menke. Obtained abundantly where there are currents, 

 in sand runs or along rocky shores and on the rocky shoals near the outer islands. 

 Occurs also but not plentifully in muddy bays. Spire long and tapering, apex 

 usually eroded away, whorls 8-9, flattened, suture not deeply impressed, distinct 

 carina at lower edge of whorl. Aperture small and rhomboidal; prolonged ante- 

 riorly into a slight groove, closed by an operculum borne on upper side of foot. 

 Unlike the long spired species of Lymnaea which inhabit sheltered situations, this 

 form which is also long spired is well-adapted to exposed places because of its 

 strong heavy shell. In contrast with the Lymnaea also, it, when detached, does 

 not float on the water, but sinks at once into deeper water. A quite variable 

 species. Varies in length and stoutness of spire, usually high and slender, often 

 quite short and stout, color dark brown, shaded with green, light green or white. 

 In young, carina well-marked; in adults, no carina on body whorls; in younger, 

 color much darker. Feeds on diatoms and desmids. (PI. XI, Fig. 16). 



Goniobasis haldemani, Try on; (not positively identified.) Occurred on shady 

 beach along exposed shore. Few obtained. More slender and elongated, whorls 

 more rounded than in livescens. No carina and the color white tinged with green. 



Family amnicolidae. 



Represented by three species, all belonging to the genus Amnicola. 



Genus Amnicola. 



Of the three species obtained here, A. limosa is the most abundant. All 

 occur in weedy places either with mud or sand bottom. A. limosa is secured 

 also on the rocky shores of even the outer islands and A. limosa and lustrica were 

 obtained in deep dredgings. Operculate. 



Amnicola limosa, Say; obtained on weeds in sand channels or muddy bays, 

 on rocky shores and in dredging at 20 fathoms or more. Very abundant, tentacles 

 long and constantly in motion. The jet-black eyes placed at outer bases of ten- 



