120 TEIRESTRIAL AIR-BREATHING MOLLUSKS. 



The surface of the shell is raised in numerous rib-like folds, frequently anas- 

 tomosing; longitudinal ribs reticulate the surface and render the folds so cre- 

 nulated that in certain lights the shell appears as if ornamented with strings of 

 beads. This peculiar character disappears at the base of the shell, and is re- 

 placed by revolving lines and regular lines of accretion. 



Genitalia not observed. 



Z. milium is described by Morse as having 68 rows of 17 — 1 — 17 teeth on its 

 lingual membrane, with only 2 perfect laterals. The next six teeth are shown 

 to be bifid, not only the one or two transition teeth, but the decided marginals. 

 I have also drawn the membrane of this species (PI. III. Fig. M). I found 18 — 

 1 — 18 teeth, with 3 laterals. The peculiarity of the lingual of this species is 

 the great development of the central tooth. 



The jaw also is peculiar in having vertical channels worn upon its anterior 

 surface, extending down to the cutting margin as in the following species. 

 These channels are probably worn by the greatly developed central tooth 

 of the lingual membrane. I do not agree with Morse in considering the great 

 development of the central tooth and the channels on the jaw as generic 

 characters. 



Zonites Binneyanus, Morse. 



Shell umbilicated, subglobose, transparent, almost colorless, shining, smooth, 

 with microscopic wrinkles of growth and still more delicate oblique wrinkles : 

 spire not much elevated ; whorls about 4, rounded, 

 lg ^_ gradually enlarging, the last globose, broadly umbilicated 



below ; aperture oblique, subcircular, large ; peristome 

 simple, acute, extremities not approaching, that of the 

 columella subreflected. Greatest diameter, 4 mill.; height 

 2 mill. 



Hyalina Binneyana, Morse, Journ. Portl. N. H. Soc, I. 13, Figs. 25, 26 ; PI. 

 II. Fig. 9; PI. VI. Fig. 27 (1864). — Tryon, Amer. Journ. Conch., II. 252 

 (1866). — W. G. Binney, L. & Fr.-W. Sh., I. 39 (1869). —Gould and Binney, 

 Invert, of Mass., new ed., 400 (1870). 



Helix Binneyana, Mokse, Amer. Nat., I. 542, Fig. 32 (1867). 



Southern part of Maine ; Tawas Bay, Michigan ; Massachusetts. It may be 

 considered peculiar to the Northern Region. 



Jaw very broad, arched, ends attenuated, bluntly rounded; concave margin 

 with a small rounded median projection, on either side of which are two smaller 

 projections (Morse). 



Lingual membrane described by Morse with 60 rows of 23 — 1 — 23 teeth ; 

 centrals tricuspid ; laterals 2, bicuspid, but with a third cusp-like process on the 

 inner side ; marginals aculeate. On PI. III. Fig. I, I give a figure of the teeth 

 on a membrane examined by me, kindly furnished by Mr. Anson Allen, of 



