favorable to their introduction and dispersion. ‘The fact that 
three of the seven specimens common to both continents occur 
fossil in the loéss of Iowa, and another, Vztrea hammonis 
(Strom), has been found associated with the remains of a 
mastodon in Berrien county in this state, would seem to sub- 
stantiate this theory. 
The following species have been found in the Post-plei- 
ocene deposits in this state: 
Polygyra albolabris maritima  Zonttoides arboreus (Say ). 
Pils. Strobilops labyrinthia (Say). 
“s thyroides (Say). Succinea retusa Lea. 
S monodon (Rack). Vertigo gouldi Binn. 
Pyramidula alternata Say. Carychium exiguum (Say.) 
Vitrea hammonis (Strom). 
Of the twelve species given by W. G. Binney as being univer- 
sally distributed over North America, all are found in Michi- 
gan, and nearly all of them are among our most common and 
abundant forms. ‘They are: 
Pyramidula striatella (Anth).  Vilrea hammonis (Strom). 
Punctum pygmaeum (Drap). ‘* indentata (Say). 
Flelicodiscus lineatus (Say). Zonttoides nitidus (Miill). 
eae pulchella (Miill). bs arboreus (Say). 
Pupa muscorum (Le ) a minusculus (Binn). 
Conulus fulous (Miill).* es milium (Mse). 
Of the species considered by the same author as characteristic 
of the Northern Region, twelve are represented in our fauna, 
VIZ: 
Vitrina limpida Gld. Pyramidula asteriscus (Mse). 
V2trea binneyana (Mse). Vertigo gouldi Binn. 
[S) Verred (Mise). ‘* bollesiana Mse. 
Zonitordes exiguus (Stimp). ‘¢ — ventricosa Mse. 
Gastrodonta multidentata Cochlicopa lubrica ( Miill). 
(Say). Sphyradium edentulum 
Acanthinula harpa (Say). (Drap). 
Five of these have apparently a general distribution over 
the state, viz: 
Gaslrodonta multidentata Cochlicopa lubrica (Miill). 
(Say).  Sphyradtum edentulum 
Vertigo gouldi Binn. (Drap). 
ec) * wentricosa Mise. Zonitotdes exiguus (Stimp.) 
Vitrea binneyana (Mse)., and Zonitordes exiguus (Stimp. ) 
have both been reported from Kent county. This, however, 
* Since the recent revision of this genus by Pilsbry this species would scarcely 
fall within this category. 
6 
