HYALINA. 397 



the Rio Chama in New Mexico ; from Florida to Great Slave Lake ; 

 also ill Washoe County, Nevada ; in Montana and California. It is 

 also said to occur in Cuba, and in Guadaloupe. 



This shell has very little to distinguish it except its very simple 

 structure. It is like H. ccllaria except in its smaller size. Helix 

 itidentala has also a similar size and external appearance ; but is 

 known by its distant, impressed, radiating lines. Ferussac sup- 

 posed it to be a variety of H. lucida, Drap. ; but our shell has the 

 umbilical region more excavated, and the umbilicus larger ; there 

 is also one whorl less in shells of the same size, so that the surface 

 appears less crowded. The aspect of the two shells, on comparison, 

 is sufficiently diverse. H. electrina has also one whorl less, and has 

 a much more polished appearance. 



Occasionally a thickening of the shell seems to take place at in- 

 tervals, so as to produce an opaque appearance. 



Hyalina electrina. 



Fig. 111. 



Shell small, depressed, pellucid, fragile, amber colored ; whorls four, conspicu- 

 ously wrinkled by the lines of growth ; aperture rounded ; lip simple ; umbili- 

 cated. 



Helix electrina, Gould, Inv. 183, fig. Ill (1841 ). — Bixxey, Best. Jonrn. Nat. Hist. iii. 



423, pi. 22, fig. 2 (1840) ; Terr. Moll. ii. 286, pi. 29, fig. 1. -De K.\y, N. Y. Moll. 



30 (1843).— Adams, Vermont Moll. 161 (1842). — W. G. Binney, Terr. Moll. iv. 



117. — Morse, Amer. Nat. i. .542, fig. 31 (18t7). 

 Hdix pura, Alder, teste Pfeiffer, Mon. Hel. Viv. iv. 83. 

 Helix Janus, Adams, (olim) Shells Vt. Am. Journ. Sc. [1] xl. 273 (1841). 

 Zonites radialulus. Reeve, Br. Land and Fr. Sh 50, fifj. (1863). 

 Zonites striaiida, Moquin-Tandox, Moll. Fr. teste Beeve. 

 Helix viridida, Menke, Syn, Math. 2d ed. 127 ; see also Mai. Blatt. viii. 92. 

 Hyalina electrina, Morse, Journ. Portl. Soc. i. 13, fig. 23 ; pi. 6, fig. 24 (1864). — Tryon, 



Am. Journ. Conch, ii. 251, pi. 4, fig. 25 (1866). 



In the size, depressed-conical shape of the upper surface, the 

 number of whorls, and the rapid enlargement of the lowest 

 whorl, this shell corresponds with H. indentata. It differs 



in its darker, smoky horn color, its constant umbilicus, its 

 rather thick and shining lip, and its whitish wrinkles, 

 which, instead of being remote, are crowded as in other 

 species. From H. arborea it differs in having one whorl 



>- '^ H. electrina. 



less, the last one dilating ; its apex not being depressed, 

 its thinner, more shining structure, and its somewhat smaller um- 

 bilicus. In H. arborea the outer lip has a flexuous curve, but is 



