PACIFIC COAST SPECIES. 117 



Helix Cohmhiana, Lea, Am. Phil. Soc. Trans., vi, 89, pi. xxiii, fig. 75; Obs., li, 89 

 (1839) ; in Troschel, Arch. f. Nat., 1839, ii, 221.— De Kay, N. Y. Moll., 46 

 (1843).— Pfeiffer, Mod. Hel. Viv., i, 343; in Chemnitz, ed. 2, i 3:i2, pi. 

 Iviii, figs. 10-12 (1846).— Reeve, Cou. Icon., No. 692 (1^52).- Binney, Terr. 

 Moll., ii, 169, pi. v.— W. G. Binney, Terr. Moll., iv, lo; L. & Fr.-W. Sh., i, 

 150 (1869). 



Selix laliosa, Gould, Proc. Bost. Soc. Nat. Hist., ii, 165 (1846); U. S. Expl. Exped. 

 Moll., 67, fig. 35(1852); Terr. Moll., ii, 170, pi. xiii, a, fig. 1.— Pfeiffer, Mon. 

 Hel. Viv., i, 343 (included in Columbiana in vol. v). 



Mesodon Columbiana, Tryon, Am. Journ. Conch., iii, 46 (1867).— W. G. BiNNEY. 

 Terr. Moll., v, 333. 



A species of the Pacific Province, ranging from Sitka and Fort Simp- 

 son (latitude 54^ 40') to Santa Cruz, in California (latitude 37° 20'), 

 along the coast. 



Animal slender, eye-peduncles and tentacles much elongated. Color 

 pale ferruginous, with a lilac tint, darker on the neck. Whole surface, 

 even the eye-peduncles, marked with coarse, elliptical granules, in lon- 

 gitudinal series ; no marginal border. 



There is a variety with a well-developed parietal tooth. 



I formerly had difficulty in separating certain forms of Mesodon Co- 

 lumhiamis, Lea, and Stenotrema germanwn, Gould, until I had received, 

 through the kindness of Mr. Henry Hemphill, specimens of both species, 

 preserved in alcohol, from several distinct localities. An examination 

 of their soft parts has proved that in the jaw and genital system there 

 exists a specific difference readily detected. This difiereuce appears to 

 be constant, as I have observed it in one specimen, with parietal lamina 

 and quite depressed, of Golunibianufi^ from San Leaudro, Cal., and three 

 from another locality. In germanmn I also have found the charac- 

 ters constant, having examined four specimens, one from Astoria, the 

 other three from a separate locality. 



In the jaw the distinction is in its general outline and in the 

 size and frequency of the ribs on the anterior surface. In germannm 

 the jaw is slightly arcuate ; the ribs are about 11 in number, broad, 

 crowded, with narrow interstices only, generally resembling tlie jaw 

 found in Stenotrema. In Columbianus the jaw is r.iorc arched, the ribs 

 are less numerous, about 8, narrower, much more separated, and more 

 decidedly produced on either margin, as usual in Mesodon. (For figures 

 of the jaw of each see Ann. N. Y. Lye. Nat. Hist., X, Plate. XIV.) 



In the genitalia the difference lies in the genital bladder. This 

 organ in Columbianus (Terr. Moll., Y, Plate XI, Fig. I) is clavate, short, 



