THE NAUTILUS. 67 



P. rotnndatum Prime. " Lake Superior," Prime and Currier ; 

 cited also by De Camp. 



P. variabile Prime. Apparently ranges over the State as I have 

 it from Wayne, Washtenaw and Roscommon Counties. Cited also 

 by De Camp. 



P. ventricosum Prime. Cited by Miles and De Camp. 



P. noveboracense Prime. Cited by De Camp from Cass County. 



P. oeqidlaterale Prime. Detroit and Rouge Rivers, Wayne 

 County. 



OBSERVATIONS ON THE HELICOID GROUP CHAROPA AND ALLIED 



FORMS. 



BY HENRY A. PILSBRY. 



A striking illustration of the vast breadth of the intellectual 

 horizon open before the zoologist is the fact that notwithstanding the 

 large number of scientists, only comparatively rarely do two or 

 several workers publish simultaneously and independently upon 

 absolutely the same aspect or branch of the same special subject. 

 When such a coincidence happened in the times of our predecessors 

 it often gave rise to jealous rivalry, as in the ease of Conrad and 

 Lea, and earlier, Say, Rafinesque and Hildreth. In these newer 

 days, cases of simultaneous discoveries in science should, and usu- 

 ally do, lead to an opposite result — to the most helpful and happy 

 friendship and sympathy between naturalists, even though half the 

 globe separates them. 



These thoughts are brought to my mind by receiving, in the last 

 Australian mail, proof-sheets of an article by my friend, Charles 

 Hedley, of the Australian ]\Iuseum, Sydney, N. S. W., entitled 

 " Observations upon the Cbaropidoe." In this article Mr. Hedley 

 discusses many of the points considered in my " Observations on 

 the Helices of New Zealand," published in the September Nautilus ; 

 and also extends his notes to the Australian and Polynesian forms. 

 I cannot i-efrain from quoting from his paper these passages: 



" Widespread throughout Australia and Polynesia is a group of 

 land shells which, varying greatly among its members, yet appears 

 clearly distinguishable from other orders by the small size of its 

 species, their cancellated sculpture, in which stout ribs are a promi- 



