Mollusca of Middlehury, Vt. and Vicinity. 277 



Cyclas. 



C. elegans, nob. Rather common in a swamp five miles north 

 of this village. One specimen occurred at Burlington. 



C. rhomhoida, Say. Very abundant in Lake Champlain. This 

 is the only species which I have seen in the open waters of the lake. 



C. partumeia, Say. Common in swamps, 



C. calycidata, Drap. In company with Valvata sincera, this 

 species was found quite plenty. It has also been found in this 

 town v^ery numerous in a cavity one yard in diameter in a swamp, 

 and it is remarkable that not one could be found elsewhere. Dr. 

 Mighels has found it occurring plentifully in Maine. That the 

 same species of Cyclas should occur so abundantly in this coun- 

 try and in Europe, may seem incredible. But the coincidence 

 is so exact, that were specimens from both continents mingled, 

 I do not think that they could be separated. 



The descriptions of native species of this genus are so unsatis- 

 factory, that I do not venture to affix names to two other species, 

 of which one is the largest and the other the least of American 

 species. 



General Remarks. — Of the thirty two terrestrial species enu- 

 merated above, three certainly, and possibly four, are also widely 

 distributed in Europe; while of the forty five aquatic species, 

 identity with those of Europe appears only in a single instance. 



Lake Champlain appears to be the most eastern limit on this 

 continent of the entire family of Melaiiiana, and is also on the 

 boundary between two provinces of the Naiades. Unio alatus, 

 U. gracilis, U. rectus, U. vetitricosKS, and U. htteolus, which are 

 common through the western states, occur in its waters, and wiih 

 the exception of U. rectus, plentifully, but are not found any far- 

 ther eastward. U. comprcssus, and Alasmodonta rugosa, western 

 species, also occur in its vicinity, but have not been found east of 

 the Green Mountains. U. complanatus, an eastern species, com- 

 mon as far at least as Eastport, Maine,* occurs abundantly in Lake 

 Champlain. The family of Limnseana do not observe this boun- 

 dary.! 



* Whence I have specimens, through the kindness of J. Ray, M.D. of that place. 



t Of most of the species enumerated in this article, I have duplicates, and also 

 of upwards of 100 marine species of the shells of Maine and Massachusetts, which 

 I shall be happy to exchange for native or foreign shells. 



Vol. XL, No. 2.— Jan. -March, 1841. 36 



