tJie Shells of Maine. 325 



Besides the above, I have received several specimens of an 

 Unio from Monmouth, concerning whose specific characters I 

 am much perplexed ; it may prove to be new. 



Genus Alasmodon. Say. 



A. arcunta, Barnes. This species is plentiful all over the 

 State. The largest and best specimens are found in small 

 sluggish streams, in muddy places. Dr. Gould remarks that 

 he has never found it near the sea-board. I have. It occurs 

 plentifully at Cape Elizabeth, near the sea. 



Specimens from different localities differ much among them- 

 selves, beinsf more or less curved, or elongated, and some are 

 perfectly straight, differing in no respect from U. sinuosa and 

 elongata of Lamarck, from Germany and France. With Mr. 

 Lea, I believe them to be identical. 



A. undulaia. Say. This is extensively distributed over the 

 State, and plentiful. 



A. marginata, Say. Often found, but not plentiful. 



An extraordinary variety of this, or (which is more proba- 

 ble to me) a new species, occurs at Easrport. Tlie late Dr. 

 C. J. Ward thought it might be A. radiata, Con. Not having 

 had an opportunity to compare it with that species, I am still 

 compelled to leave it in doubt. 



Genus Anodox. Brug. 



A. caiaracta, Say. Widely distributed over the State. In 

 ponds it is large and comparatively thick, resembling speci- 

 mens from South Carolina. In sluggish, muddy streams, it is 

 more abundant, but of a smaller size, and mucli tliinner. 



A. marginata, Say. Elongated specimens of this species, 

 resembling, externally, A. ftrussaciatia, Lea, occur at Aor- 

 way, Oxford county. I doubt the propriety of separating it 

 from the preceding species. It differs no more from it than 

 many established species differ among themselves, nor half as 

 much as acknowledged varieties of U. camplanatus. 



A. impVicata, Say. The only locality where this species is 

 known to exist in the State, is in a pond near Eastport. This 



