XXI. NOTES OX THE LAXD-SHELLS OF THE ISLAXDS 



AT THE WESTERX END OF LAKE ERIE AXD 



DESCRIPTIONS OF NEW VARIETIES. 



By George H. Clapp. 



INIany of the larger shells of these islands show distinct insular 

 modification, so distinct in fact as to make them readily recognizable 

 when once seen. Others are indistinguishable from the mainland 

 forms, and this is particularly true of the shells of Put-in Bay, where 

 there seems to have been no change in the species we found. 



Both Dr. Walker and I\Ir. Goodrich, who have carefully gone over 

 these shells, and to whom I am indebted for valuable suggestions, 

 agree with me in considering the forms described below as worthy of 

 varietal rank. 



I. Pyramidula solitaria strontiana var. now 



Shell very heavy, coarsely striate, uniform straiv-color ic'itJwut a 

 trace of bands. Most specimens show traces of impressed spiral lines. 

 This variety is much more elevated, heavier, and smaller than the 

 typical banded form from the mainland, and, as it is found in many 

 of the older collections of North American land-shells, the locality 

 being given as "Strontian Island, Lake Erie," I have thought it well 

 to perpetuate the name, although the island is now "officially" known 

 as Green Island. 



We collected several hundred specimens on our visit to the island, 

 July 3, 1915, and thousands could easily have been gathered. 



Ninety-nine mature shells, that is those showing a thickening of the 

 lip, were measured with the following result: 



Diam. 24.3, Alt. 17.66 mm., Index, —,72.65 average, 



76.36 largest, 

 75.56 smallest, 

 78.85 most elevated, 

 66.00 " depressed. 



Variation in diam. from 22.5 to 27.5 or 5 mm. 

 " alt. " 16.0 " 21.0 " 5 " 



Ninety-five shells varied in diam. from 23.0 to 26.5 or 3.5 mm. 



Ninety-four alt. " 16.0 " 19.0 " 3.0 '* 



532 



