OF CONCHOLOGY. 161 



ON THE LINGUAL DENTITION OF LIMNiEA APPRESSA, 

 SAY, AND LIMNJBA MEGASOMA, SAY. 



BY THOMAS BLAND AND W. G. BINNEY. 



LlMNyEA APPRESSA. 



We are indebted to Mr. J. G. Anthony for the specimen of 

 IAmncea appressa, Say, from which we extracted the jaws and 

 lingual membrane here described. The specimen was preserved 

 in alcohol at the Museum of Comparative Zoology. It was re- 

 ceived from Lake Champlain. 



On page 28 of Part II of Land and Fresh-water Shells of North 

 America, there is a description and figure of the lingual mem- 

 brane of Limnced jin/idaris, Say, which is synonymous with 

 Limncea appressa, both of these forms being identical with IAm- 

 ncea stagnalis of Europe. On page 155 of the same work is a 

 figure of the membrane of a specimen of L. stagnalis, from the 

 Lake of Geneva. 



The form of the teeth from several different parts of the mem- 

 brane before us differ so widely that we see no specific distinc- 

 tion in the figures referred to, however much at first sight they 

 may appear to differ from the figures we here give, or from each 

 other. 



Jaws three, as usual in the genus, one upper, long, narrow, 

 arcuate ; two lateral, long, narrow, curving inwards. 



Lingual membrane long and broad, composed of numerous 

 curving rows of about 40 — 1 — 40 teeth each. 



Centrals subconical, long, narrow, excavated and sometimes 

 bilobed at base, thence narrowing gradually upwards to the 

 apex, which is bluntly rounded, and recurved into a simple, 

 obtuse beak. Laterals shorter than the centrals, subtriangular, 

 their outer side being somewhat parallel to the side of the cen- 

 trals, while the inner side is rapidly cut away towards the base, 

 which is very narrow and straight ; their top horizontal, irregu- 

 larly waved, bearing a decided stout blunt prominence near its 

 inner extremity, the whole broadly recurved into a large, long, 

 oblique beak ; this beak is bifid, the divisions about equal in 



