60 THE NAUTILUS. 



to the group of islands belonging to Ohio and Ontario, of which 

 only two, Put-in-Bay and Green (formerly Strontian) have 

 appeared in previous conchological literature. Lists of the land 

 shells of seven islands are given with a resum6 of the geological 

 history of the islands during successive stages of glacial time. 

 The exceptional interest of these faunas as indices of the rate of 

 evolutionary change, giving definite data on the question of the 

 age of well-marked insular races, is alluded to. The paper 

 forms an introduction to the following one. 



NOTES ON THE LAND-SHELLS OF THE ISLANDS AT THE WESTERN 

 END OF LAKE ERIE AND DESCRIPTIONS OF NEW VARIETIES. By 

 George H. Clapp, (Annals Carnegie Mus. X, 1916). The new 

 forms are as follows: 



Pyramidula solitaria strontiana, Green Island. 



Pyramidula solitaria roseoapicaia, North Harbor Island. 



Pyramidula solitaria mynesites, Mouse Island. 



Pyramidula alternata eriensis, Middle Sister and other Islands. 



Polygyra profunda strontiana, Green, North Harbor, Middle 

 Sister Island. 



Polygyra albolabris goodrichi, Middle Sister Island. 



"Many of the larger shells of these islands show distinct 

 insular modification. . . . Others are indistinguishable from 

 the mainland forms, and this is particularly true of the shells 

 of Put-in-Bay island, where there seems to have been no change 



in the species we found." The divergence from mainland forms 

 of the species is notably different on different islands, as in the 

 cases of Pyramidula solitaria strontiana, and roseoapicata. Dif- 

 ferent species are diversely modified, so that the differentiation 

 of the races does not appear directly related to the insular con- 

 ditions, though such relations might become obvious on further 

 investigation. It may be a case of isolation products, due to 

 different mutations occurring in the several colonies. Important 

 facts for evolution might follow further study of the physical, 

 faunal and floral conditions of the islands. At all events, the 

 little exploration by Messrs. Clapp, Goodrich and Walker has 

 opened up an interesting field for research. 



A form similar to P. alternata eriensis is found in some of the 

 islands off the New England coast. An excellent plate of shell- 

 figures and diagrams showing variation curves illustrate the 

 paper. H. A. P. & C. W. J. 



