36 



LAND AND FRESH- WATER SHELLS OF N. A. [PART II. 



Fig. 42. 



Hah, Newport, Rhode Island : Col. Totten, United States Army. My 

 cabinet and cabinet of Col. Totten. Diam. .30, length .55 of an 

 inch. 



This is one of the most delicate and fragile of the genus 

 Limnma which I have seen. It is allied to i\Ir. Say's L. colu- 

 mella; but may at once be distinguished by the compression of 

 the superior part of the body whirl, which causes an acute 

 angle in the superior part of the aperture. Under a rather 

 powerful lens, some of the specimens may be perceived to have 

 very minute revolving striae. The aperture is two-thirds the 



length of the shell, and is inflated at the inferior part. The fold of the 



columella is delicate and incurved. {Lea.) 



Limnsea casta, Lea. — Shell subfusiform, rather thick, closely striate, 

 yellow, perforate ; spire rather elevated, acuminate ; sutures 

 impressed ; whirls six, convex ; aperture large, ovate. 



Hdb. Poland, Ohio : Dr. Kirtland. My cabinet and cabinets 

 of Dr. Kirtland, and T. G. Lea. Diam. .30, length .58 of an 

 inch. 



The columella of this species is remarkably straight, and 

 being reflected, causes the lower part of the aperture to be 

 slightly effuse. The last whirl is wrinkled. The aperture is 

 *more than half the length of the shell. It is allied to L. de- 

 sidiosa, Say, but is a smaller species, has the spire more ex- 

 serted, and a less curved fold. The perforation is very small. 



Dr. Kirtland kindly sent me many specimens several years since. (Lea.) 



Fig. 44 represents, at oue view, tlie various forms which have 

 been described as distinct species. 



Fig. 43. 



Fig. 44. 



L. coarctata. L. casta. L. Tnacrostoma. 

 Fig. 45. 



L. columella. 



L. chalyhea. L. atrigona. 



Fig. 45 represents the lingual 

 dentition of the species. There 

 are eighty rows of about seventy 

 teeth each. 



Dr. T. R. Ingalls, of Greenwich, 

 N. Y., to whom I am indebted for many specimens of shells and 

 much valuable information, wrote me in 1860 the following curious 

 note reirarding L. columella. His words are — 



Lingual dentition of L. columella. 



