THE NAUTILUS. ! 27 



The largest of the three specimens, a dead individual, measures: 

 altitude, 16 mm.; greater diameter 27,1 mm.; lesser diameter 

 21.2 mm. 



No race of Epiphragmophora tudiculata appears to have been 

 described from that general region. The general form and the 

 weak malleations of the surface distinguish this race from the 

 other members of the tudiculata group and strongly suggest 

 Epiphragmophora traski, but the nuclear characters as well as the 

 other sculptural features all ally it with the tudiculata complex. 



MOTES ON VABIATION IN PLANOKBIS CAMPANULATU3 SAY, FBOH 

 BLUE SEA L&KE, QUEBEC. 1 



BY E. J. WHITTAKER. 



Variability in Planorbis campamdatus is much less common 

 than it is in a related species, P. trivolvis, in which variation 

 with reference to size and aperture of the shell has resulted in 

 many varieties being established by conchologists. The shell 

 in P. campanulatus may vary in size in certain localities, due to 

 differences in bottom environment and food supply, but in the 

 same area the form is apt to be constant. While at Blue Sea 

 Lake, Wright County, Quebec, about eighty miles north of 

 Ottawa, in the summer of 1918, the writer secured a large series 

 of P. campanulatutSj in which several well-marked deviations 

 from the normal type were observed. 



PREVIOUS OBSERVATIONS. 



Various observations have been made on variation in this 

 species among which are the following: 



Tryon 2 remarks: " The plan of the spiral in this genus (i. e. 

 Planorbis) is such as to yield readily to pressure, hence mon- 

 strosities are rather frequent. This consists of a tilting-up of 

 the whorls on one side, or even a conical elevation of the spire. 

 The smaller forms appear to be most liable to this distortion." 



'Published by permission of the Director of the Geological Survey of 

 Canada. 



' J Tryon, Geo., Jr., Manual of Conchology, vol. 3, p. 106. 



