HELICINID &. 235 
near the end rapidly descending and slightly detached from the 
penultimate whorl; aperture very slightly campanulate ; labrum 
slightly reflected, rounded, not scalloped; umbilicus of mo- 
derate size, with the spiral lamella excessively developed, and 
soldered by its exterior edge to the last whorl, forming over 
the umbilicus a large arch, which has an opening much larger 
than the aperture of the shell. Height 0.065, greatest breadth 
0.118, least br. 0.095 inch. 
Stoastoma Agassizianum, Adams, Contrib. to Conch. n. 9, p. 158; 
Pfr. Pneum. Mon. p. 327. 
Hab. Jamaica. 
20. StoastoMA PHILIPPIANUM. 
Shell subdiscoidal, convex above, pale horn-coloured, subtrans- 
parent; surface smooth and shining; spire moderately and con- 
vexly elevated; whorls 34, slightly convex, with a moderately- 
impressed suture, last whorl regularly rounded over the peri- 
phery, very slightly detached from the penultimate whorl near 
the aperture; aperture slightly campanulate; labrum slightly 
produced beyond the labium, not scalloped ; labium in its upper 
half a little detached from the penultimate whorl; umbilicus 
of moderate size, with the spiral lamella excessively developed 
and usually soldered by its exterior edge to the last whorl, 
forming over the umbilicus a large arch, which has an opening 
rather larger than the aperture of the shell. Height 0.055, 
greatest breadth 0.09, least br. 0.075 inch. 
Stoastoma Philippianum, Adams, Contrib. to Conch. n. 9, p. 158; 
Pfr. Preum. Mon. p. 328. 
Hab. Aikendown in Westmoreland, Jamaica. 
II. TROCHATELLA. 
Operculum not spiral, semioval, flat, pale, more or less solid. 
Shell top-shaped, or globose-conic; aperture semioval, rather 
triangular; columella nearly flat, not sending backward any 
basal callus, sometimes uniting the margins of the peristome 
by a very thin deposit, which is not diffused. 
Helicina, § 1, Gray, Zool. Journ. i. 66, 1828. 
Trochatella, Swainson, Malacol. p. 337; 1840, Pfr. in Zeitschrs. f. M. 
1847, p. 152; 1848, p. 82; Chemn. ed. ii. P. 18, p. 4; Adams, 
Contrib. to Conch.; Pfr. Pneum. Mon. p. 328. 
Oligyra (part), Gray, in Proc. Z. S. 1847, p. 182. 
