404 HELICID.E. 



teeth. Plates long and narrow, becoming narrower as they ap- 

 proach the sides of the membrane. Plates transparent. Denti- 

 cles light horn color, central plate largest with one small rounded 

 denticle, laterals with two equally short rounded denticles, those on 

 the verge of the membrane having three minute denticles. 



Hyalina multidentata. 



Shell depressed, pellucid ; whorls six, narrow, slightly convex ; aperture semi- 

 lunate, narrow; peristome acute; two or more rows of minute teeth within; 

 uniliiiicus very small. 



IMix vmhidentata, Binnet, Bost. Journ. Nat. Hist. iii. 425, pi. 22, fig. 5 (1840) ; Terr. 

 Moll. ii. 258, pi. 48, fig. 3. —Adams, Vermont Moll. 161 (1842). — Chemnitz, 2d 

 ed. ii. 202, pi. 101, figs. 9- 12. — Pfeiffer, Mon. Hel. Viv. i. 184. — W. G. Binney, 

 Terr. Moll. iv. 123. — Keeve, Con. Icon. No. 729. — Mouse, Amer. Nat. i. 543, fig. 

 33 (1867). 



Hi/alina multidentata, Morse, Journ. Portl. Soc. i. 15, fig. 31 ; p. 61, fig. 30 ; pi. 6, fig. 32 

 (1864). 



Gastrodonta multidentata, Trton, Am. Journ. Conch, ii. 258, pi. 4, fig. 43 (1866). 



Shell umbilicated, depressed, sub-planulate above, very thin, pel- 

 lucid ; epidermis smooth ; shining ; whorls six, nar- 

 '^' ' row, slightly convex, increasing l)ut slowly in diam- 

 eter, 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, radiating from the 

 umbilicus, are seen through the shell, within the base 

 of the last whorl. Greater diameter, three and one 

 H. multidentata. fourtli mill. ; Icsscr, three mill. ; height, one and a half 



Enlarged. ..-. 



milumetres. 



Maine, Vermont, 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 whorl, radiating 

 from the centre. One row is usually so near the aperture 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. 



Hyalina line at a. 



Fig. 103. 



Shell small, discoidal, green ; whorls four, with fine, elevated, parallel revolv- 

 ing lines ; aperture narrow, semi-lunar ; lip simple ; throat with two or more 

 pairs of teeth ; umbilicus broad and deep. 



