with numerous equidistant, parallel, raised lines revolving upon 

 them; suture much impressed; aperture remote from axis, self- 

 lunate, narrow, not expanding; peristome acute, thin; umbilicus 

 wide, forming a concave depression of the base, each volution 

 visible to the apex; within the aperture, on the external circum- 

 ference, are placed from 1 to 3 pairs of minute, conical, white 

 teeth, the first pair in sight when looking into the aperture, the 

 others more remote: greater diameter 3.5, lesser 3, hight 1.5 mm. 

 Hartland, Vermont, common. Oakland, Cal., Idaho, New 

 Mexico, Texas. Now placed in the genus Helicodiscus. 



9 Hyalina minuscula 



Shell umbilicated, minute, depressed-convex; epidermis whit- 

 ish; whorls 4, convex, not increasing rapidly in diameter, with 

 microscopic wrinkles; suture very distinctly impressed; aperture 

 nearly circular; peristome thin, acute; umbilicus large, not 

 spread, deep, and exhibiting the volutions; base rounded, colu- 

 mella with a thin callus; greater diameter 2.5, lesser 2.3, height 

 1 mm. 



Hartland, Vermont, rare. This has a wide range, south to 

 Yucatan, Mexico, Florida, Texas, Arizona, California, Japan, Cuba, 

 and Porto Rico. 



10 Hyalina exigua 



Shell broadly umbilicated, depressed, pellucid, greenish horn 

 color, marked with delicate revolving lines, and distant longi- 

 tudinal ribs obliquely decussating the incremental striae; spire 

 scarcely elevated, apex free from striae; whorls 3.5, convex, the 

 lapt rounded, widely umbilicated below; aperture oblique, trans- 

 versely rounded, remote from axis; peristome simple, acute, its 

 columellar extremity not reflected; greater diameter 2.5, height 

 0.5 mm. 



Hartland, Vermont, rare. Canada, New York, Michigan. 



11 Hyalina viridula 



Shell umbilicated, depressed, thin, fragile; epidermis pale, or 

 brownish horn color, wrinkled, shining; whorls 4, the last rapidly 

 enlarging toward the aperture; aperture transversely rounded; 

 peristome simple, its edge rather thickened, not acute; umbilicus 

 small, but well marked and constant; greater diameter 5, lesser 

 4.6, height 2 mm. 



Hartland, Vermont, common; a circumpolar species common 

 to three continents, reported from Portland, Oregon, Utah, Ari- 

 zona, New Mexico, and the shores of the Gulf of Mexico. 



12 Hyalina fulva 



Shell imperforate, subcorneal thin, pellucid; epidermis 

 smooth, shining, minutely striated, amber-?olored; whorls 5 or 

 6, rounded, very narrow; suture distinct and deep; aperture trans- 

 verse, narrow; peristome simple, acute; base convex; umbilical 

 region indented, umbilicus closed; greater diameter 4, lesser 3.5, 

 height 3 mm. 



Hartland, Vermont, rare; a circumpolar species common to 

 three continents. Sitka, Alaska; Lake Tahoe; San Gorgonio 

 Pass, Riverside Co., Cal.; Nevada; Texas; Florida. 



13 Hyalina imiltidentata 



Deoreseed, thin, yellowish horn-color, smooth, shining, peliu- 

 cid; whorls 6, slowly increasing, suture impressed; aperture trans- 

 verse, narrow, lip extending to the perforated axis, base convex, 



