406 HELICIDiE. 



Animal (of 31. concava}, upper surface grayish ; eye-peduncles 

 long, slender, bluish, base dirty white, color reddish-orange, poste- 

 rior extremity slightly tinged with the same ; foot narrow, twice as 

 long as the diameter of the shell, tail pointed, scarcely reaching be- 

 hind the shell ; other characters as in Helix. Carnivorous. 



Jaw crescentic, ends sharply pointed, anterior surface striated ; 

 concave margin smooth, with a median projection. 



Lingual membrane with numerous arched rows of aculeate, re- 

 curved, thorn-like uncini ; centrals simple, conical, pointed ; laterals 

 w^anting; 23-1-23 teeth in each transverse row. 



Macrocyclis concava. 



Shell depressed, whitish or greenish horn colored; whorls five, finely striate; 

 aperture rounded; peristome sub-reflected; umbilicus wide and deep. 



Ildix concava, Sat, Joiini. Acad. ii. 159 (1821); Binney's, ed. 20. — Binnet, Bost. 



Journ. Nat. Hist. ill. 372 (1840), excl. pi.; Terr. Moll. ii. 163, pi. 21. — Adams, 



Vermont Moll. 159 (1842), excl. Syn. Vaiicouverensls. — De Kay, N. Y. Moll. 33, 



pi. 2, fig. 15 (1843).— Pfeiffer, Mon. Hel. Viv. iv. 159. — W. G. Bixnet, Terr. 



Moll. iv. 65. — Leidt, Terr. Moll. U. S. i. 258, pi. 12, figs. 9-11 (1851), anat. — 



Morse, Am. Nat. i. 412, figs. 26, 27 (1867). 

 Helix planorboides, Ferussac, Hist. t. 82, fig. 4. — Pfeiffer, Mon. Hel. Viv. i. 200; 



SymboliB, ii. 37 ; Chemnitz, 2d ed. ii. 164, pi. 95, figs. 17 - 19 ; pi. 154, fig. 45 (1851). 



— Reeve, Con. Icon. 674 (1852). — Deshayes in Per. i. 87. 

 llelix dissidens, Deshayes in Per. Hist. i. 97, pi. 84, figs. 1, 2. 

 Macrocjiclis concava, Morse, Joum. Portl. Soc. i. 12, pi. 5, fig. (1864). — Tryon, Am. 



Journ. Conch, ii. 245, pi. 3, fig. 8 (1866). 



Shell depressed, very slightly convex on the upper surface ; epi- 

 dermis whitish horn color, sometimes with a tinge of 

 '^' ' green ; whorls five, above flattened, below rounded, 



finely striate obliquely, and sometimes with micro- 

 scopic revolving lines, the outer whorl spreading a 

 little towards the aperture ; suture rather deeply im- 

 pressed ; umbilicus wide, deep, exhibiting all the 

 volutions to the apex ; aperture rounded, somewhat 

 flattened above, its edge frequently tinged with red- 

 dish-brown ; peristome sub-reflected at its columellar 

 extremity, simple above, and in some specimens con- 

 isiderably depressed near its junction with the outer whorl ; col- 

 umella with a thin callus, the edge of which connects the upper and 

 lower extremities of the peristome. Greater diameter, twenty-one 

 mill. ; lesser, sixteen mill. ; height, seven millimetres. 



