208 Descriptions of New Species of JPupadw. 



Lateral plates tridentate, inner denticle largest. TJncine minutely 

 notched. 



Shell. — Umbilicate, ovate conic, smooth, polished ; apex 

 obtuse ; suture deep ; whorls four, convex ; aperture semi- 

 circular, with five teeth, one prominent on the parietal margin 

 two smaller on the columellar margin, and two prominent 

 within, contracting the aperture at the base ; peristome widely 

 reflected, the right margin flexuose, within thickened and 

 colored. 



Length .07 inch ; breadth .045 inch. 



Station. — On dead leaves and twigs in wet places. 



Distribution. — Throughout Maine ; Concord, N. H. ; Mo- 

 hawk and Greenwich, ]ST. Y. 



Remarks. — This species has been confounded with Isthmia 

 ovata, which it very much resembles in its general contour ; it 

 is one-fourth smaller however, has one whorl less, the columellar 

 margin is more circular. In I. ovata the aperture is armed 

 with from seven to eight teeth, always having two and some- 

 times three on the transverse margin ; while this species has 

 five teeth, one only being found on the transverse margin. It 

 can readily be distinguished from I. ovata by these differences 

 and its smaller size. The late Dr. Ingalls of Greenwich, 1ST. Y., 

 noticed this species among a lot of I. ovata collected by him, 

 but regarded it as an extreme variety only of the latter species. 

 Its wide distribution and constant characters indicate its specific 

 value. 



