114 AMERICAN JOURNAL 



OBSERVATIONS ON AN ABNORMAL SPECIMEN OP 

 PHYSA GYRINA. 



BY GEOEGE W. TRY ON, JR. 



Plate 10, Figs. 9, 10. 



The sliell first figured is from Grand Rapids, Mich., and 

 was sent to me by J. A. McNeil, Esq., of that place, where the 

 species occurs abundantly. The monstrosity consists in the 

 upper portion of the whorls being round-shouldered or geni- 

 culate, with a deep immersed suture, making the spire some- 

 what scalariform, but short. 



It is well known that Paludina scalaris, Jay, a Florida 

 species, was described from a single specimen in the author's 

 cabinet, and that no other specimens have since occurred. 

 The singular deformation of the present species suggests to 

 me the probability that scalaris also is a more exaggerated 

 example of the same aberrant formation. 



A copy of Dr. Jay's original figure (fig. 10) is given for 

 comparison. 



