94 SEVENTH REPORT. 



Polygyra clausa was originally listed by Sager in his Catalogue of 1839. The citations in 

 Miles' Catalogue of 1S62, and in Currier's Catalogue of 1868 were probably based on Sager's 

 citation. There are no Michigan specimens in the Currier collection at the present time. 

 Its occurrence in Kent comity has been verified by the inspection of a specimen collected 

 there by Mr. W. Miller of Grand Rapids. No specimens of this species from Genesee County 

 are to be found in any of the existing collections. The following note from the late Dr. 

 Manly Miles is of interest in this connection, "Sager's listing of H.. clausa as a Michigan 

 species was repeatedly verified in the early collections of shells in Genesee County by mem- 

 bers of the Flint Scientific Institute. Unfortunately these specimens have been scattered 

 and lost. As Binney in Terr., Moll., II. p. 109 makes H. mitchelliana a synonym of H. 

 clausa, no attempt was made to separate the two forms and it. may be that we labelled 

 '* clausa" in some cases that would now be placed under '^mitchelliana" 



The present range of Polygyra elerata seems to be limited to the western part of the state. 

 The records from Berrien and Kent counties have been verified by the inspection of speci- 

 mens. That for Osceola County was reported by Mr. W. Miller of Grand Rapids. The 

 Washtenaw County record is based on dead shells from recent deposits. It has not been 

 found living there. 



We have, as yet, no authentic record of Polygyra pennsylvanica having been found liv- 

 ing in Michigan. The Monroe County record is based on specimens purchased from Ward 

 of Rochester and labelled "Petersburg, Mich." No information as to the source of these 

 specimens could be obtained. Mr. Jerome Trombly, the only collector known from that 

 locality, has never found it. The Wayne County record is based on a single dead speci- 

 men found by the writer on the shore of Bois Blanc, one of the islands at the mouth of 

 the Detroit River. A careful search failed to find it alive on the island, which is compar- 

 itively small and has no timber left on it. Whether this specimen was brought do\\Ti from 

 some locality further up the Detroit River or some of its tributaries, or is a stray " ballast" 

 shell, is therefore wholly uncertain. 



Polygyra sayii is a boreal species and is no doubt confined to the northern part of the 

 state It is evidently of rather rare occurrence in the state, as most of the records are 

 based on single specimens. As it has not yet been found in the Upper Peninsula, and is 

 not cited from Minnesota by either Grant or Sargent, Michigan probably represents its 

 extreme western range. 



The distribution of the four species of Triodopsis grouping around P. jmlliata as shown 

 on Plate IV, is apparently very peculiar in the entire absence of any records from the south- 

 western part of the state. But as three of the species are listed by Baker from the Chicago 

 Area and all of them are of general occurrence in Indiana according to Daniels, the proba- 

 bility is that lack of records from this portion of the state is due rather to the ill luck of 

 the collectors, than to the actual non-existence of these species in that di-strict. The pov- 

 erty of our knowledge of the fauna of the counties lying north of the Saginaw-Grand Valley 

 renders it impossible to say whether the apparent restriction of the range of all the species 

 of this group to the north is a real one or not. 



The distribution of the species of Stenotrema in Michigan, as shown on Plate V, is quite 

 interesting. 



Polygjira hirsuta has probably a general distribution across the southern part of the 

 state, although the record is lamentably deficient. It has not, as yet, been recorded from 

 north of the Saginaw-Grand Valley. 



The typical form of Polygyra monodon was originally described in 1822 from specimens 

 collected in Alpena County. This is probably the earliest record of any Michigan species. 

 It is one of our most abundant species wherever found, but has not yet been recorded from 

 the northwestern part of the lower peninsula, nor from the upper peninsula. 



On the other hand the varietal form P. monodon fraterna as shown on Plate I, is one 

 of the forms, whose occurrence in all parts of the state seems unquestionable. 



The main conclusion to be drawn from the records, as they now stand, is the absolute 

 necessity for more facts before any reliable results can be deduced in regard to the dis- 

 tribution of the species of this interesting genus in Michigan. Any data bearing on the 

 range of any of the species would be acceptable and may be forwarded to the writer for 

 permanent record in the census. 



Detroit, Mich. 



