APPENDIX. 263 



west Territory, and may be found i» plenty crawling 

 upon the rocks near the shores. They vary in size from 

 those found in the eastern states, being less than half as 

 large. 



P. armigerus, nob. St. Peter and Red rivers, com- 

 mon. 



P. bicarinatus, nob. North-west Territory, rather com- 

 mon. 



LYMNEUS. 



L. megasomus. Large, dilated suboval ; spire, short, ra- 

 pidly diminishing, acute ; whorls about five, rounded, ob- 

 tusely wrinkled across; body-whorl large, the wrinkles 

 very obvious; suture deeply impressed; aperture sub- 

 ovate, much longer than the spire, within chesnut-brown ; 

 columella white. 



Length more than one and six-tenths of an inch. 



Length of the aperture more than one inch. 



Greatest diameter one inch. 



This remarkably large and fine species was found in 

 Bois blanc Lake, North-west Territory, by Dr. Bigsby, to 

 whom I am indebted for specimens. The colour is brown- 

 ish, sometimes lineated across the body whorl with dull 

 greenish and pale ochraceous ; and the chesnut-brown co- 

 lour of the interior of the shell, combined with its large 

 dimensions, distinguish this species from all others yet dis- 

 covered in this country. PI. 15, fig. 10. 



L. emarginatus, nob. from Lake Namakan, north of 

 Lake Superior, collected by Dr. Bigsby. 



L. elongatus, nob. Rainy Lake and Seine river, Dr. 

 Bigsby. 



L. desidiosuSf nob. Falls of Niagara. 



