50 



LAND AND FRESH-WATER SHELLS OF N. A. [PART L 



spaces between each two sets. They are apparent in the 

 youngest as well as in the oldest specimens, and continue to be 

 formed from time to time, so long as the shell increases in size. 

 They probably mark regular periods of growth. 



Fig. 80. 



Hyalina 



rrmUidentata, 



enlarged. 



Hyalina milltidentata, Binney. — Shell umbilicated, depressed, 

 sub-planulate above, very thin, pellucid ; epidermis smooth, shining ; 

 whirls six, narrow, slightly convex, increasing but slowly 

 in diameter, delicately striated, beneath smoother ; suture 

 impressed ; aperture semi-lunate, narrow ; peristome 

 acute ; umbilicus very small, rounded, pervious ; base 

 convex, indented around the umbilicus ; two or more 

 rows of very minute, white teeth, r.adiating from the 

 umbilicus, are seen through the shell, within the base 

 of the last whirl. Greater diameter 3|, lesser 3 ; height 

 1^ mill. 



Helix multidentata, Binney, Bost. Journ. Nat. Hist. Ill, 



425, pi. xxii, f. 5 (1840) ; Terr. Moll. II, 258, pi. 



xlviii, f. 3. — Adams, Vermont MoUusca, 161 



(1842).— Chemnitz, 2d ed. II, 201, pi. ci, f. 9-12. 



— Pfeiffek, Mon. Helic. Viv. I, 184. — W. G. 



Binney, Terr. Moll. IV, 123.— Reeve, Con. Icon. no. 729.— Mokse, 



Amer. Nat. I, 543, f. 33 (1867). 



Hyalina multidentata, MoRSE, Journ. Portl. Soc. I, 15, f. 31, p. 61, f. 30; 



pi. vi, f. 32 (1864). 

 Gastrodonta multidentata, Tbton, Am. Journ. Conch. II, 258, pi. iv, f. 43 

 (1866). 



Maine, Yermont, New York, Ohio ; also Lower Canada. 



There are from two to four rows of very minute, delicate, 

 white teeth, on the lower side of the interior of the last whirl, 

 radiating from the centre. One row is usually so near the aper- 

 ture as to be seen within it with the aid of a microscope ; the 

 others are more or less remote : each row contains from five to 

 six distinct teeth. They are visible through the shell. 



Jaw arcuate, broad in centre, greatly attenuated and blunt at 



