THE NAUTILUS. 127 



Pupa armifera Say. 



Pupa coiitracta Say. 



Vertigo ovata Say. 



Vertigo gouldii Binn. Quite abundant apparently, and exhibiting 



some considerable variation in size. A single albino example is 



included, of which Dr. Sterki writes "This is a very interesting 



and valuable specimen ; the only true albino among many thousand 



specimens of our Vertigos I have seen. " 



Vertigo ventricosa elatior Sterki. Not heretofore known from 



Michigan. 



Vertigo pentodon Say. Vertigo curvidens Gld. 



Ferussacia subcylindrica L. 



Succinea oblivua Say. Succinea peoriensis Wolf. 



Succinea avara Say. Succinea sp. 



Succinea ovalis Gld. Succinea sp. 



There are four forms of Succinea in the collection, which group 

 around S. ovalis Gld. as a type. The first is the form usually called 

 ovalis characterized by the short; rather blunt spire, elongated body 

 whorl and effuse aperture. The second is the peoriensis of Wolf, a 

 very widely extended form in Michigan and easily separated from 

 the "ovalis" by reason of the shorter body whorl and more nearly 

 oval aperture, which though somewhat narrowed posteriorly lacks 

 the patulous expansion anteriorly so characteristic of the former. 

 The third resembles ovalis in the shape of the aperture, but is a 

 more slender shell and has the spire more elongated than either the 

 preceeding forms. It appears to range generally over the State and 

 is the same form noticed as "S. higginsi Bid." in my catalogue of 

 Michigan shells (Naut. VI, p. 19). 



The fourth form is quite remarkable. Having the general shape, 

 characteristic of the group, it far exceeds them all in dimensions, 

 equalling in length a good sized S. obliqua Say. These shells were 

 labeled by Dr. Lathrop as " S. sillimani Bid.?" They agree sub- 

 stantially in form and size with figures of that species given by 

 Biuney. Some individuals, however, have the spire more produced, 

 resembling in that respect the figures of S. hawkinsi Bd. ; but the 

 suture is not impressed to the extent represented in that species. 

 None of them have the blunt apex, which seems to be characteristic 

 of S. Imydeni W. G. Binn., though fully equalling that species in 

 size. Cockerell (Naut. VI, pp. 23 and 29) refers all these forms to 

 the S. elegans Risso of Europe. It is possible that these specimens 



