Mollusca of Middlebury, Vt. and Vicinity. 271 



Deshayes remarks, (Lam. An. sans. Yert. 2nd edit.,) in common 

 with some others, it estabhshes a passage between the two gen- 

 era, and proves the uselessness of one of them. 



Pupa. 



P. armifera, Say. Of this species, not before known this side 

 the Alleghany Mountains, (Gould, Monog. Bost. Journ, Nat. Hist. 

 Vol. Ill, p. 401,) I have found a very few specimens in Bridport 

 on the borders of Lake Champlain, and Prof. Benedict has found 

 it at Crown Point. 



P. badia, noh. This species was discovered in company with 

 the preceding by Prof. Benedict. Dr. Gould (op. cit.) remarks 

 that it is " almost precisely like" P. marginata, Drap. That 

 species has a narrower aperture and wider umbilicus. It is quite 

 possible however that a comparison of numerous specimens may 

 establish their specific identity. 



P. albilabris, WardJs letter. This species is well known as 

 Say's Cyclostoma marginata. The late lamented Dr. Ward, of 

 Roscoe, Ohio, ascertained that it was a Pupa, and, as Say's spe- 

 cific name had been pre-occupied in this genus, proposed for it the 

 name which we have given. A few specimens only in this re- 

 gion have been found by Prof. Benedict. 



P. ovata — syn. Vertigo ovata, Say. This species has been 

 mistaken by some for P. modesta, Say, but a specimen with all 

 the teeth fully developed leaves no doubt in my view of the cor- 

 rectness of others, who have regarded it as P. ovata. It is rare 

 in this vicinity, but is more common near Boston. 



P. contracta, Say. This species is found quite plentifully. 

 Mature specimens vary considerably in size. 



P. exigua, Say. This very neat little species is rather common. 



P. milium, Gould. This is the most minute shell, which has 

 been described in this country. Twelve mature specimens to- 

 gether weighed less than .06 gr., or .005 gr. each. The Delphi- 

 nula serpiiloides, nob., the least of the marine shells of New Eng- 

 land, weighs precisely twice as much. The dimensions of Pupa 

 milium are, length .06 in., breadth .03 in. The Helix pygmcBa, 

 Drap., according to Turton, (Land and Fresh Water Shells of 

 Great Britain,) is .05 in. broad, and Deshayes remarks (op. cit.) 

 that it is "unedes plus petites especes connues." This Pupa 

 therefore is probably the most minute of known shells, with the 

 exception of the microscopic Cephalopods. 



