. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 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 reflect
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 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., XLVII. 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 broad
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