Bay. ‘These facts would seem to indicate an extension of the 
Boreal Zone beyond its present described limits. 
In the southern part of the state, with possibly one 
exception, there is nothing to indicate from a molluscan point 
of view, any distinction between the Transition and Upper 
Austrial Zones. The fauna extends with substantial uni- 
formity from lake to lake. While it is apparently the fact 
that the mollusca, both land and fresh water, are more 
abundant both in species and individuals in the western part 
of the state than they are in the eastern, owing, no doubt, to: 
more favorable conditions of environment. the difference is 
solely one of degree and not that any considerable number of 
western species are wholly absent from the eastern counties. 
That the larger number of species reported from Kent is the 
result of more thorough collecting is shown by the fact that 
with the exception of Vertigo morsez Sterki, and Gastrodonta 
demissa (Binn.), every one of its fiftytwo species has been 
reported from one or more of the eastern counties. There are 
a few species, however, which seem to form an exception to 
this rule, and, if their present apparent distribution is con- 
firmed, would seem to be confined substantially to the limits 
of the Upper Austral Zone as outlined by Merriam. These 
are: 
Polygyra inflecta (Say). Vertigo milium Gld. 
es profunda (Say). Grastrodonta ligera (Say). 
cs hirsuta (Say). Pyramidula solitaria (Say ). 
These species are reported from Kent in the western part 
of the state, and in one or more of the south-eastern counties 
of Oakland, Macomb, Wayne, Washtenaw, Monroe and 
Lenawee. 
Three other species, Strobzlops ajffiinis Pils., Gastrodonta 
suppressa (Say), and Pupordes marginatus (Say) range as far 
north as Genesee county on the east. Noone of them, as yet, 
have been reported from the interior of the state lying 
between the counties above mentioned, nor east of Kent county 
in the Saginaw-Grand valley. Polygyra elevata (Say), another 
common species of this zone a little further south, bas thus 
far been found only in Berrien, Kent and Osceola counties, 
although it has been reported from recent deposits in Wash- 
tenaw county. Pyramidula solitaria (Say) is peculiar in hav- 
ing also been found in Chippewa county in the upper penin- 
sula, but has not been reported from any locality between 
that and Kent county. Gastrodonta demzssa (Binn.), 1s 
another species common further south, which has been found 
at Grand Rapids, but not elsewhere, as yet, in our limits. 
8 
