108 THE NAUTILUS. 



place. I have examined the river for many miles, but have never 

 found any of the shells elsewhere. 



NOTES ON PHYSA GYRINA. 



BY A. A. IIINKLET. 



A small spring, the basin of which has been dug to the depth of 

 three feet or more and walled with rock to the surface of the ground, 

 has been the home of Physa gyrina for many years. The water 

 spreads out some as it leaves the basin and then drains into a ditch 

 nearby. 



Until this year, this colony has been nearly typical of the species. 

 On April 28th I noticed that there was quite a number of good- 

 sized shells around the borders of the basin, and on examining them 

 was surprised to find an unusual roughened or malleated surface 

 amounting to folds and humps on some individuals. The roughened 

 surface was confined to the last stage of growth, which rarely ex- 

 tended back much over half the whorl. On this date egg-masses 

 were numerous on and under leaves, which were in the shallow 

 water. All mature shells I could find were taken for my cabinet. 



On May 8th a few more mature shells were found, at this time 

 most of the eggs had hatched and the minute shells were very 

 numerous. 



November 26th a visit to the spring in the morning surprised a 

 pair of kildee plovers feeding in the shallow water, no Physa were 

 visible around the borders, a few were found under leaves, but the 

 shells could be seen on the bottom of the basin, and where the water 

 issues from the rock they were piled up several deep. 



Afternoon I returned with a net and took some fifty of the 

 largest, most of these have two callus deposits or bands, and a few 

 three ; these bands are not the same on any two shells, they may be 

 close together or half a whorl apart, the last one may be the borders 

 of the outer lip or as far as one-fourth of a whorl back. The lines 

 of growth may be a little stronger than usual, but none of these 

 shells show the roughened surface of those taken seven months ago. 

 It will be interesting to see what develops by the time the year is past. 



