30 PLANORBIS ARMIGERUS. 



Color whitish, with a very pale tinge of 

 brownish. 



Geographical Distribution. Inhabits Eu- 

 rope, New England, "Lake Superior to Sas- 

 katchewan." 



OBSERVATIONS. 



The shell is so closely rolled, that but little of 

 the inner turns appear; and when perfect, is 

 easily recognised by the hirsute exterior. Dr. 

 Gould compares ours with the European shell, 

 but in assuming it as distinct, says it is thinner, 

 with the last whirl increasing more rapidly, and 

 that "it maintains its yellowish-brown color, 

 whereas P. albus assumes a spermaceti, or still 

 w^hiter appearance. The lines too, disappear 

 almost entirely, when the epidermis is gone." 



PLANORBIS ARMIGERUS, Say. 



Plate 4.— Figs. 11—15. 



P. testa brunnea, supra plana; subtiis profunde umbili- 

 cata: anfractibus 4 rotundatis; suturis inipressis: apertura 

 intus 6.dentata. 



