48 



LIMNEA DESIDIOSA? 



Plate 13.— Figs. 16—18. 



SYNONYMS AND REFERENCES. 

 L. obrussa, Say. Journ. Acad. Nat. Sci., vol. v. p. 123. 



DESCRIPTION. 



"Shell oblong, rather slender, pale yellowish 

 testaceous: whorls five, slightly rounded: apex 

 acute: suture deeply impressed: aperture not 

 dilated, within pure white: columella with the 

 sinus of the fold very obvious. 



"Lister, pi. 114, fig. 8?" 



OBSERVATIONS. 



Found by Say in a small rivulet above Phila- 

 delphia. His specimens in the Academy's col- 

 lection, agree very nearly with some collected 

 by myself from ditches along the Susquehanna, 

 and which I consider as a marked variety of 

 L. desidiosa. They are generally smaller and 

 narrower than this species; and the posterior 

 extremity of the aperture has a stronger ten- 



