the Shells of Maine. 335 



Genus Planorbis. Mull. 



P. trivolvis, Say. Dr. Milliken has found a few specimens 

 in a pond at Unity. 



P. lentus, Say. Found at Unity, in company with P. tri- 

 volvis. It differs in no respect from Vermont specimens, 

 which Professor Adams has confounded with P. corpulentus, 

 of the Western States, which is certainly distinct. 



P. bicarinatus, Say. This species occurs in most of our 

 ponds and brooks where the water is quiet, but I am not aware 

 that it is abundant anywhere. 



P. campanulatus, Say. This abounds in all parts of the 

 State. 



P. armigerus, Say. Mr. True has found this in plenty at 

 Monmouth. It occurs at Bangor of larger size than at Mon- 

 mouth. 



P. elevatus, Adams. I have detected a few specimens of 

 this species ? in a spring within the limits of this city. 



P. deflectus, Say. I have frequently found this shell in 

 ponds, clinging to bits of floating wood, &c., but I am not 

 aware that it is anywhere plenty. 



P. exacutus, Say. Solitary specimens are often found in 

 most of our collections of fresh water. At Norway, Oxford 

 county, I once found it in plenty, ensconced in the crevices of 

 old decayed oak logs, lying at the margin of a pond. I think 

 it always prefers oak wood. 



P. parvus, Say. This species is often seen in great num- 

 bers, resting upon the stocks of small aquatic plants, in shallow 

 water, where it is still and warm. 



Genus Physa. Drap. 



P. hetcrostropha, Say. This species abounds in gi'eat pro- 

 fusion in all parts of tiie State. Quiet pools seem to be its 

 favorite habitations ; it however occurs abundantly in rapid 

 streams. 



P. ancillaria, Say. This has been found in various parts 

 of the State. I am indebted to Mr. A. W. Longfellow for 



