LIMNEANA. MOLLUSCA. LIMNiEA. 215 



want of auricles at the base of the tentacula, and the simple, entire 

 edge of the mantle. This latter point I did not notice, when the ani- 

 mal was before me. 



Mr. Say describes the animal as black, and spotless above and be- 

 low ; tentacula with a white ring at base. He must have observed 

 them at a more advanced age than any I have seen living ; or else 

 the species observed are different. 



Genus LIMNtEA, Lam. 



Shell thin^ oblong or turreted, last whorl large ; aperture large, 

 rounded before, narrowed and acute behind, outer lip sharp, inner 

 lip forming a fold on the pillar, and usually spreading over it. 

 Animal with short, triangular tentacula. 



LiMNiE'A COLUMe'lLA. 



Shell ovate, fragile, transparent, pale-green; whorls four, the 

 three upper ones minute, lines of growth distinct, undulated by 

 revolving lines ; aperture ample ; umbilicus minute. 



Figure 144. 

 State Coll., No. 68. Soc. Cab., No. 1302. 



Lymnae'a columella. Say ; J^icholson's Encyc. {Jlmer. ed.), iv. Journ. Acad. Kat. 



Sc, 1. 15. 

 Lymnae^us navicula, Valenc. ; Rccueil d'Obs. de ZooL, par Humh. et Bonpl., ^51. 



Shell ovate, ventricose, extremely thin and fragile, transparent, 

 of a pale-greenish or yellowish color, the apex acutely pointed ; 

 whorls four, of which the last is much inflated, and composes 

 nearly the whole shell ; the upper ones are very small, forming an 

 acute apex ; surface with conspicuous and nearly regular lines of 

 growth, minutely waved by revolving lines, some of which are 

 distinctly elevated ; suture slightly impressed ; aperture large, 

 four fifths the length of the shell, generally somewhat dilated ; lip 

 very sharp, ending with a small curve behind ; on the left margin 

 the edge is slightly turned over a minute umbilicus, and forms a 

 considerable fold ; a thin, closely adhering enamel stretches 



