28 THE NAUTILUS. 



Philadelphia in a pond about one mile south of Ojiontz, Montgomery 

 County, Penna., along Old York Road. A possibility of accidental 

 mixture of specimens was thought to exist, and no published record 

 made of it. 



Upon Mr. E. G. Vanatta's learning that I lived near the auricularia 

 locality, he mentioned the case to me and I felt confident that the 

 station referred to must be that known as Dobbin's pond at Old York 

 Road and Ashbourne Road. He asked me if I would not sometime 

 examine the pond with tlie hope of verifying the Jacob record. I 

 accordingly did so on May 22nd of this year and found, associated 

 with Planorhis antrosus Conrad, an abundance of a large LymncBa 

 which proved to be the desired L. auricularia, as was verified the 

 following morning by Dr. Pilsbry and Mr. Vanatta when I brought 

 in living material. 



Dobbin's Pond was doubtless at one time well kept, since it is 

 situated on private property, but for many years the estate has been 

 largely left to take care of itself, and consequently much debris of 

 refuse, dead leaves and sticks has collected in it. A delta formation 

 of considerable extent occurs at the inlet stream. Few, if any, hu'ge 

 water-plants, like pond-lilies, occur, but there is an abundance of 

 algal growth, and pond-scums cover much of the surface. 



The Lymncea is a very striking species, both because of the large 

 size of full-grown individuals, and, of the conspicuous dark mottling 

 of the mantle on a light yellow ground as seen through the shell on 

 the younger individuals. The mottling was commonly obscured in 

 the large specimens because of algal growth and dirt. Most of the 

 animals, especially the half-grown ones, were found crawling around 

 in shallow, quiet water on the muddy bottom, along the sides of the 

 delta. The large individuals were generally found attached to 

 floating logs or sticks, and one was seen .sticking to grass stems 

 hanging into the water. The majority of the specimens seen were 

 doubtless half-grown individuals from the past season. The shells 

 were found to measure on the average about 17 mm, X 12 mm. 

 The largest shells measured about 28 mm. X 21 mm., but some of 

 Jacob's collection are as large as 30 mm. X 24 mm. One specimen, 

 found dead, has the aperture very beautifully and widely flaring but 

 in most of the material this is not well-developed, or else has been 

 broken away. 



Except for a very possible solution, suggested by Mr. Vanatta, 



