HELIX PLAGIOrTYCHA. 17 



conical form and two obscure narrow brown bands around the mid- 

 dle of the body-whorl. 

 H. ALBERSIANA PfeifFer. PL 31, figs. 19-21. 



Umbilicate, subturbinate-depressed, thin, brownish corneous, with 

 one or two faint peripheral brown bands sharply, rather irregularly 

 and coarsely rib-striate ; spire low-conical, slightly obtuse, apex 

 smooth; sutures moderately impressed; whorls 4$-5, moderately 

 convex, the last rounded at the periphery, very deeply deflexed at 

 the aperture, somewhat flattened and subconstricted behind the per- 

 istome on the base ; aperture very oblique, truncate-oval ; peristome 

 thin, well expanded, especially below, where it is thickened within 

 by a linguiform callus ; terminations joined across the parietal wall 

 in adult specimens by an elevated lamina. 



Alt. 7-9, diam. maj. 12-14 mill. 



Hayti; Inagua, Bahamas. 



If. albersiana PFR. P. Z. S. 1851, p. 147. Monographia, iii, p. 

 231. REEVE, Conch Icon. f. 300. 



This form may be known by the coarse, rough striation and 

 in adult shells by the elevated lamina joining the terminations of the 

 peristome. The base of the aperture has a more or less developed 

 thickening callus inside. Many specimens are less elevated than the 

 one figured. There are generally two narrow faint brown bands at 

 the periphery, with a light fascia between them. 



H. LOXODON Pfeiffer. PI. 12, figs. 44-46 ; pi. 19, figs. 43, 44. 



Perforate, depressed, thin, but more solid than the preceding forms, 

 slightly translucent, pale brownish-corneous, sometimes with two ill- 

 defined, narrow, brown fasciae around the periphery, a light band 

 between them ; regularly elegantly and densely costulate-striate ; 

 spire low-conical, apex concolored, smooth, slightly obtuse ; sutures 

 moderately impressed ; whorls about 5, convex, the last rounded at 

 the periphery, deeply descending anteriorly ; on the base behind the 

 periphery, constricted. Inside the umbilicus (when it is not too nar- 

 row to see in) the last whorl has a spiral furrow or groove a charac- 

 ter not shown by H. albersiana. Aperture oval or oval-truncate, 

 extremely oblique ; peristome straight or slightly expanded above, 

 outer and basal margins expanded, the latter reflexed, partly or 

 almost wholly concealing the narrow umbilicus. The basal margin is 

 sometimes nearly straight, sometimes decidedly curved toward the 

 upper lip ; it bears an oblique callus ridge inside ; parietal callus 

 very light, transparent, its edge never elevated, 

 2 



