THE MOLLUSC A OF GEORGLAN BAY 99 



SESSIONAL PAPER No. 39b 



nata canadensis the shell is smaller, shorter and smoother, the whorls fewer and 

 more convex and the sutures are more impressed. (PI. X, Fig. 7). 



L. emarginata canadensis. Sowb. ; very abundant on cleanrocky shores, especially 

 of the outer islands. Found also on sand and pebble bottom. Corresponding to 

 its exposed position and in contrast to the other species, L. palustris, it is thick- 

 shelled with shortened spire and is of light coloration. It is a medium-sized species 

 (adult length 20-25mm.) and is usually recognized easily by its light horn colour 

 and malleated surface. The spire is shorter than the aperture, the whorls well- 

 rounded, 5-6 and the sutures distinct. The aperture is large and ovate with a 

 somewhat flaring lip and with reddish varical thickenings usually prominent im- 

 mediately behind it. A white callus spreads over the body-whorl and covers but 

 does not close the deep slit-like umbilicus. Usually with several whitish or reddish 

 varical thickenings. Identified as this variety by Mr. E. G. Vanatta. As it occurs 

 at Go Home it is quite variable, especially in surface malleation, thickness of the 

 shell, height of the whorls and length of the spire. Thinner shells show more definite 

 malleations. Its food consists of algae. It has been taken from the stomach of 

 the whitefish, Coregonus clupeiformis. (PL X, Fig. 14). 



L. (Galba) palustris, Muller, abundant in shallow bays on the bottom or on 

 submerged vegetation, often on mud flats above the water's edge. It prefers 

 moderately high temperatures. It is easily recognized by its narrow elongated 

 form, dark colour and by the aperture which is usually shorter than the spire. 

 Lip somewhat flared. Surface of shell variable, smoother in island pools, usually 

 roughened by coarse lines of growth in muddy bays. Sometimes malleated. 

 Color brown to almost black, darker in pools, often whitish due to erosion. In 

 young, color darker and lip not flared. Distinguishable from L. emarginata 

 canadensis in the more slender elongated form, narrower and shorter aperture, 

 longer spire, darker color and distinct habitat. It feeds upon the filamentous 

 green algse, diatoms and desmids. Found in the stomachs of whitefish. (Pi. X, Fig. 8) . 



L. (Pseudosuccinea) columella, Say. Common on lower surface of lily-leaves 

 in stagnant, muddy bays. Easily recognized by its expanded and oblique body 

 whorl, its long aperture, expanded anteriorly, rather sharp-pointed spire and its 

 delicate shell-structure. Lines of growth prominent. Its elongated form and es- 

 pecially its delicate shell are adaptations to its protected habitat. Food consists 

 of diatoms, desmids and other green algse. (PI. XI, Fig. L5). 



L. (Acella) haldemani (Deshayes) Binney: Found on the lower surface of lily- 

 leaves in well-sheltered muddy bays in late summer. Observed in but two situa- 

 tions, both of which were removed from open water and were especially well-pro- 

 tected. Several specimens secured in each situation. Diligent search failed to 

 reveal any during the early summer and nothing was found to indicate their habitat 

 during this period. These observations agree in their main features with Kirk- 

 land's account as given by Baker ('11). Those secured were, however, considerably 

 removed from deep water; none were observed in the approaches to the bays, 

 neither were any secured in dredging. This is the most striking Lymnaea of the 

 region. Its extremely slender form, long spire, oblique, flattened whorls, long 

 nan-ow aperture, sharply angular at the posterior end and its thin transparent 

 396—71 II 



