134 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



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 3j, lesser 3 mill. ; 

 height, \\ mill. 



Helix multidentata, BINNEY, Bost. Journ. Nat. Hist., III. 425, PI. XXII. Fig. 5 

 (1840) ; Terr. Moll., II. 258, PI. XLVIII. Fig. 3. ADAMS, Vermont Mollusca, 

 161 (1842). CHEMNITZ, 2d ed., II. 201, PI. CI. Figs. 9- 12. PFEIFFER, 

 Mon. Hel. Viv., I. 184. W. G. BINNEY, Terr. Moll., IV. 123. REEVE, 

 Con. Icon., No. 729. MORSE, Amer. Nat., I. 543, Fig. 33 (1867). 

 I Hyalina midtidentata, MORSE, Journ. Portl. Soc., I. 15, Fig. 31, p. 61, Fig. 30 ; 

 PL VI. Fig. 32 (1864). W. G. BINNEY, L. & Fr.-W. Sh., I. 50, Fig. 80 

 (1869). GOULD and BINNEY, Inv. of Mass., eJ. 2, p. 404 (1870). 



Gastrodonta multidentata, TRYON, Am. Journ. Conch., II. 258 (1866). 



A species of the Northern Region, noticed in Maine, Vermont, New York, 

 Ohio ; also Lower Canada. 



For a figure of the rosy-white, thread-like animal, see Boston Journ. Nat. 

 Hist., HI. PI. XXII. Fig. 5. 



This species possesses characters so marked that it, at first, is not likely to 

 be mistaken for any other. The numerous narrow whorls visible on its upper 

 and plane surface, while only one is seen below, together with its minute, round 

 umbilicus, and narrow aperture, would sufficiently distinguish it ; but there is 

 another still more peculiar character. There are from 2 to 4 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 5 to 6 distinct teeth. They are 

 visible through the shell. The transparency of the shell is so great that 

 frequently the sutures of the upper surface can be seen through it, when 

 viewed on the base. With the living animal within, the shell has a roseate 



tinge. 



' Jaw arcuate, broad in centre, greatly attenuated and blunt at ends ; concave 

 margin smooth, with a slight median projection. 



The lingual membrane examined (PI. III. Fig. N) had 14 1 14 teeth, 

 with 2 perfect laterals. Morse gives 68 rows with 15 1 15 teeth, also 2 

 perfect laterals. 



FOSSIL SPECIES OF ZONITES. 



Ztmites (Conulus) prisons, CARPENTER, Quart. Journ. Geol. Soc., 1867, p. 331, 



with Figs. Nova Scotia. 

 Helix (Zonites) margmicola, CONRAD, Am. Journ. Conch., VI. 315, PI. XIII. 



Fig. 9, 1871. Oregon Terr. 



