THE NATURAL HISTORY SURVEY. 241 



are similar, narrower, and bi- or tricuspid; the marginals are 

 low, wide and serrated. 



Distribution: Universal. 



SUBGENUS VERTILLA Moq. Tand. 1855. 

 (Angustula Sterki. 1889.) 



This group is "mainly characterized by the long and high 

 gular lamina." (Sterki.) 

 96. Vertigo milium Gould, pi. xxx, fig. 16. 



Pupa milium GOULD, Bost. Journ. Nat. Hist., Vol. Ill, p. 402, pi. iii, fig. 

 23, 1840. 



Shell: Small, subcylindrical, smooth shining; growth lines 

 very fine, a little oblique; nucleus smooth; color dark chest- 



Fig. 70. 

 VERTIGO MILIUM Gould. (Original.) 



nut; whorls five, rounded, somewhat regularly increasing, 

 decreasing to a bluntly rounded apex; sutures impressed; 

 aperture obscurely semicircular, lateral, truncated above; the 

 "circumference" of the aperture is "made up of two curves of 

 different radius uniting in the peristome, where the junction 

 causes an angle projecting inwards, the smaller curve compris- 

 ing about one-fourth part and forming the superior portion of 

 the peristome;"f aperture six-dentate as follows: two sharp, 

 projecting teeth of about equal size placed on the parietal wall 

 and dividing that region into three nearly equal parts; one on 

 the columella, large, massive, broad; a third placed on the 

 outer lip above or at the junction of the two radii, long, curved, 

 ridge-like, pointing directly between the two parietal teeth; a 

 fourth on the base of the lip, small, conical, tubercular; and one 

 large, entering, elevated, long lamina, which begins on the 

 base of the lip and curves backward until it disappears behind 

 the columella tooth (this is the "gular lamina" of Sterki); per- 

 istome white or brownish-white, reflected, the terminations 

 separated, but joined by a prominent callus; umbilicus well 

 marked, open, deep; base of shell rounded (Fig. 70). 



*Binney, Man. Amer. L. S., p. 332, 



