HELICINID&. 301 
13. ALCADIA MEGASTOMA. 
Shell depressed-globose, smooth, covered with bands of a hairy 
periostraca, shining, fuscous ; spire depressed-conoidal ; whorls 
4*, convex, last large, convex beneath; aperture rather 
oblique, semicircular; columella shortly receding, terminating 
in a very small knot, dilated backwards into a thin callus; 
peristome slightly thickened, narrowly expanded, separated 
from the columella by a small slit. Operculum rather solid, 
pale. Height 5, greatest breadth 8, least br. 6} mill. 
Helicina megastoma, Adams, Contrib. to Conch. n. 1, p. 14. 
Alcadia megastoma, Pfr. Pneum. Mon. p. 411. 
8. Thinner, pellucid, with the periostraca more distinct. 
Helicina affinis, Adams, in Proc. Bost. Soc. ii. 1846, p. 102. 
Hab. Jamaica. 
14, ALCADIA MACILENTA, 
Shell depressed, nearly discoidal, thin, very minutely punctured 
and striated, pale fuscous ; spire slightly raised, scarcely acumi- 
nated; whorls 43, scarcely convex, last broader, rather flat 
beneath ; aperture diagonal, nearly semicircular; columella 
short, terminating in a small tooth, which is curved forwards 
and thickened externally ; peristome simple, narrowly expanded, 
separated from the columella by a narrow, deep, curved slit ; 
basal callus thin. Height 33, greatest breadth 7}, least br. 6 
mill. 
Helicina macilenta, Adams, Contrib. to Conch. n. 1, p. 18. 
Alcadia macilenta, Pfr. Preum. Mon. p. 411. 
Hab. Jamaica. 
15. ALCADIA HISPIDA. B. M. 
Shell globose-depressed, thin, reddish-brown, densely covered with 
short hairs ; spire scarcely raised, slightly acuminated ; whorls 
4%, moderately convex, increasing gradually, last moderately 
convex beneath ; aperture somewhat oblique, semiovate ; colu- 
mella extremely short, terminating in a recurved, free tooth ; peri- 
stome rather simple, scarcely expanded, white internally, upper 
margin sinuate, basal margin separated from the columella by 
a sharp slit; basal callus very thin. Operculum rather mem- 
branaceous, horn-coloured. Height 4, greatest breadth 6, least 
br. 54 mill. 
DD 
