HEMITROCHUS. 175 



The jaw is strongly arched with acuminated ends, smooth anterior surface, 



and decided median prominence to cutting margin. Fig. 84 represents the jaw 



of varians. The other West-Indian species examined by me 



1 J Fig. 84. 



have the same type of jaw. 



The lingual membrane (PI. IV. Fig. L) has about 33—1—33 

 teeth; another specimen gave 43 — 1 — 43 teeth, with 17 perfect 

 laterals. The central tooth has a long, narrow base of attach- 

 ment with lower, outer angular expansions and incurved lower 

 margin. The reflected portion is only about one half the length of the base 

 of attachment, is short, and bears one short, stout cusp with an equally short, 

 stout cutting point ; the side cusps and cutting points are obsolete. The lat- 

 erals are the same as the centrals, but asymmetrical. The outer laterals, com- 

 mencing at the 11th, have a side cusp and cutting point; the inner cutting 

 point is bifid on the 16th tooth; after this the change into the marginals is 

 rapid. The marginals are low, wide, and have one broad, long, oblique, 

 bluntly bifid cutting point, the inner division the smaller, and a very much 

 shorter side cutting point. This side cutting point is also sometimes bluntly 

 bifid in the extreme marginal teeth. 



The dentition of the other species of this genus, extralimital to North 

 America, examined by me, agrees with that of this species. (See Pr. Phila. 

 Ac. Nat. Sc. 1874, 56.) 



Hemitrochus varians, Menke. 

 Vol. III. Pis. XLVI., XL VII. 



Shell subim perforate, of medium size, solid, conic-globose, delicately striate, 

 but leaving the surface smooth and shining ; the ground-»color is variable, beinc 

 white, dusky, greenish or reddish, and either plain or variously encircled by 

 dark bands ; the apex and the peristome, especially the columellar portion, is 

 always rose-red, and generally, likewise, the throat ; the spire is elevated, com- 

 posed of about 5j convex whorls, the outermost broadly rounded at the periph- 

 ery ; the base is moderately convex and perforated by a minute umbilicus, 

 nearly covered by the expanded and flattened peristome ; aperture small, ap- 

 proaching two thirds of a circle ; peristome acute, thickened within, a little 

 everted, becoming more so towards its inner junction. Greater diameter 19, 

 lesser 17 mill.; axis, 15 mill. 



Helix varians, Menke, teste Pfeiffer. — Pfeiffer, Mon. Hel. Viv., I. 238 ; 



in Chemnitz, ed. 2, II. 221, PI. CIX. Figs. 1-5. — W. G. Binney, Terr. 



Moll., IV. 51, PI. LXXVIII. Fig. 22. — L. & Fr.-W. Sh., I. 184 (1869). 

 Helix carnicolor, Pfeiffek, Symb., I. 37. — Deshayes in Fer., I. 205, PI. 



XXIX. A, Figs. 14-17. — Reeve, Con. Icon., No. 283 (1852). 

 Helix Pisana, Pfeiffer in Chemnitz, IX. Part 2, 139, t. CXXXII. Fig. 1186, 



1187. — Ferussac, Hist. 1. c. ? — Not of Muller. 



