CORRECTIONS. 



PAGE. 



4. After the references to Say's works add: 



HELIX DissiMiLis, Wood's catalogue, supplement of 1828, PI. 



vii. fig. 18. 



Add New York, Virginia, and North Carolina, to the locali- 

 ties of P. decisa. 

 8. For striata read striatis. 



8. Strike out the reference P. CARINATA, &c., and insert: 



HELIX DECISA, Wood's catalogue sup., pi. vii. fig. 17. 



9. Add Tennessee, to the localities. 



12. Last line, after "5, the young," add 6, the very young. 



Melania rufula. Shell lengthened conical, composed of 8 whirls. 

 the 4 anterior of which are convex, and those of the apex flat: 

 suture well marked: spire twice the length of the aperture: apex 

 suddenly tapered to a point: aperture ovate elliptic. Length 1 inch. 

 HAB. Lake Pepin. OBS. Distinguished from M. simplex by having 

 the peritreme level, and from M. virginica by the flattened apex. 4 



Physa fontana. Animal dark fuliginous, foot as long as the shell: 

 shell ovate, translucent, composed of 3 convex turns^ apex eroded: 

 suture well marked: labium nearly straight, with a slight fold: 

 color yellowish brown. Length \ inch. Inhabits cold springs in 

 Pennsylvania. OBS. Closely resembles P. fontinalis of Europe, but 

 the foot is shorter. 



Physa osculans. Shell oval or lengthened, translucent: whirls 4 

 or 5, slightly convex: suture well marked: aperture narrow, longer 

 than the spire, with the labium expanded far upon the body whirl: 

 columella thickened. Length i to 4 inch. HAB. Middle, Eastern 

 and Western States. OBS. This species'? bears an equal resem- 

 blance to P. heterostropha and P. gyrina. 



Ancylus parallelus. Shell brown', low, much appressed, aperture 

 oblong oval, apex subcentral. Length .15 breadth .10 in. HAB. 

 Vermont. Prof. Adams. 



Subgenus Angitrema. Shell spinous, aperture subrhomboidal; 

 with an anterior sinus. Ex. Melania armigera, Say. 



Melania costifera. Shell lengthened, composed of 8 slightly con- 

 vex turns, having numerous spiral elevated lines, crossing a series 

 of curved ribs, on all the whirls: spire twice the length of the aper- 

 ture: suture well marked: aperture ovate. Length 1 inch. HAB. 

 Illinois. OBS. The aperture is wider than in the allied species, and 

 the costae are better developed. 



