ZONITES. 115 



Linrrual membrane with 82 rows of 21—1 — 21 teeth (Morse). My specimen 

 (PI. 111. Fig. F) has about 16— 1—1 G, with 5 perfect laterals. Tliere are dis- 

 tinct side cusps as well as cutting points to the central and lateral teeth. 



Animal : head, neck, and eye-peduncles blackish, or indigo blue ; upper parts 

 bluish ; posterior parts whitish, transparent, sometimes wholly white. Foot thin 

 and narrow. It has the longitudinal furrows, but on account of the transparent 

 tissue of the foot, I find it difficult to distinguish any caudal pore. 



Helix Breweri seems to me synonymous with arboreus, but the de- 

 scription and figure from "Land and Fresh- Water Shells " is here 

 repeated. 



Shell umbilicated, depressed, smooth, shining; surface unbroken 

 by the wrinkles of growth, very light horn-color ; spire scarcely ele- 

 vated; whorls 4, flattened, the last depressed, shelving towards its 

 base ; umbilicus moderate ; aperture transversely lunar ; peristome 

 simple, acute. Greater diameter 5 mill. ; height, 2-^ mill. B?ew^^?. 



Near Lake Tahoe, California. 



Figure 32 is drawn from an authentic specimen. 



Z. arboreus is said by Gwynn Jeffreys to be nearly allied to the European 

 Z. excavatus (Ann. Mag. N. H. 1872, 245). 



Zonites viridulus, Menke. 



Vol. III. PI. XXIX. Fig. 1. 



Shell umbilicated, small, depressed, thin, fragile; epidermis pale, or brown- 

 ish horn-color, wrinkled, shining ; whorls 4, the last rapidly enlarging towards 

 the aperture ; aperture transversely rounded ; peristome simple, its edge rather 

 thickened, not acute ; umbilicus small, but well marked and constant. Greater 

 diameter 5, lesser 4f mill. ; height, 2 mill. 



Relix electrina, Gould, Invert. 183, Fig. Ill (1841). — Binney, Bost. Journ. 



Nat. Hist., III. 423, PI. XXII. Fig. 2 (1840); Terr. Moll., II. 286, PL XXIX. 



Fig. 1. — DeKay, N. Y. Moll., 30 (1843). — Adams, Vermont Mollusca, 161 



(1842). —W. G. Binney, Terr. Moll., IV. 107. — Morse, Amer. Nat., I. 542, 



Fig. 31 (1867). 

 Helix pura, Alder, teste Pfeiffer, Mon. Hel., IV. 83. 

 Helix javiis, Adams MS. (olira), Shells Vt. Amer. Journ. Soc. [1], XL. 273 



(1841). 

 Zonites radiatulus, Eeeve, Br. L. & Fr.-W. Sh., 50, Fig. (1863). 

 Zonites striatula, Moquin-Tandon, Moll., Fr. teste Keeve. 

 Helix viridula, Menke, Syn. Meth., ed. 2, 127 ; see also Mai. Blatt., VIII, 92. 

 Hyalina electrina, Morse, Journ. Portl. Soc, I. 13, Fig. 23, PL VI. Fig. 24 



(1864). — Tryon, Amer. Journ. Conch., II. 251 (1866). 

 Hyalina viridula, W. G. Binney, L. Sh., I. 34 (1869). — Gould and Binney, 

 Inv. of Mass., ed. 2, 397 (1870). 



A circumpolar species common to the three continents. In America it has 



