THE NAUTILUS. 



21 



scarcely have been made by Say, who possessed a peculiarly dis- 

 criminating sense of minute differences between shells, if he had 

 been describing the shell now known as desidiosa. The size of the 

 Philadelphia specimens (15 mill.) also corresponds pretty well with 

 the size given by Say {^^ of an inch = about 17 mill.). The most 

 convincing fact to the writer is the presence of a specimen of 

 ''desidiosa" of authors in the Philadelphia Academy marked 



*' Lymnaea , Canandaigua Lake, T. Say" (No. 58732), 



showing that tbe form usually called desidiosa is not the one so 

 called by Say. Prof. Edward S. Morse, who made the drawings ior 

 Binney's work, has been unable to give any information concerning 

 the specimen figured by Binney. 



Last summer the writer made three trips to Cayuga Lake, one to 

 lEe^south end at Ithaca and two to the north end at the town of 

 Cayuga, with the hope of securing specimens which would cor- 

 respond with Say's specimens. Three whole days were spent in 

 exploring several miles of the shore and the small creeks, and while 

 specimens of both palustris and obrussa were obtained, not a single 

 specimen was found which agreed with Say's desidiosa. The palus- 

 tris were the large, thin-shelled form and the obrussa were rather 

 small specimens, not at all like the description or specimens of 

 desidiosa. As Say gave no particular part of Cayuga Lake as the 

 identical spot in which the types were collected, it renders the task 

 of tinding locotypes well nigh impossible, since the lake is 68 miles 

 in length. 



Recently, Miss Mary Walker, of Buffalo, New York, sent the 

 writer a number of shells from Young's Quarry, Williamsville, New 

 York, which are identical with Say's specimens of desidiosa, having 

 the same number of whorls and almost the same measurements. 

 These are given for comparison: 



Say's specimens: 



Length 15.00, breadth 7.50, aperture length 8.00, breadth 3.00 

 mill. 



Length 14.25, breadth 7.50, aperture length 7.75, breadth 3.50 

 mill. 



Miss Walker's specimens: 



Length 15.00, breadth 8.00, aperture length 8.00, breadth 4.00 

 mill. 



Length 14.00, breadth 8.00, aperture length 8.00, breadth 3.50 

 mill. 



