404 
HELICINA §.'l2. 
miovalis ; columella brevis, basi subtuberculata , superne linea 
impressa, transversa marginata; perist. subincrassatum, album, 
reflexiusculum, margine supero sinuoso. — Operc. ? — Diam. 
maj. 9, min. 8, alt. 7 mill. (Coll. Nr. 77.) 
Helicina Tilei Pfr. in Zeitschr. f. Malak. 1847. p. 150. 
— — Chemn. ed. II. N. 88. p. 65. t. 2. f. 4—6. 
Habitat in Brasilia (Dr. Tile). 
Obs. Affinis H. variabili et Columbianae , huic statura et forma 
similior. 
711 143. M. troelilea Gould, f 
T. minuta , trochiformis , supra cinerea, costis acutis vol- 
ventibus 3 vel 4 (intervallis concavis , scabrosis) cincta, infra 
convexa, polita, citrina; spirae anfr. 4, ultimus ad peripheriam 
bicarinatus; apertura subtrigona; perist. leviter reflexum; 
columella ad basim angulata, callo copioso induta. — Lat. T / s , 
alt. s / 40 poll. (G.) 
Helicina trochlea Gould in Proc. Bost. Soc. 1847. p. 202 *) ; Exped. 
shells p 36. Ed. 1851. p. 99 f. 109. 
Habitat in insula Matea. 
V. Alcadia Gray. 
Operculum non spiratum, solidiusculum , semiovale, bas, 
processu dentiformi munitum. Testa heKciformis , turbinatai 
subglobosa vel depressiuscula , plerumque pilosa, basi circa 
columellam subplanulatam , strictiusculam callosa ; apertura 
triangulari - semiovalis ; peristoma magis minusve expansum, 
incisura distincta, plerumque curvata, a columella sejunctum. 
Alcadia Gray 1840. Syn. Brit. Mus. p. 134. Ed. 1842. p. 91. **) 
— - Gray in Proc. Zool. Soc. 1847. p. 182. n. 533. 
— Sow. Conch. Man. ed. II. p. 61. ***) 
*) It has the size and nearly the form of H. rupestris Pfr. and is 
distinct from all others by its well-marked, sharp, revolving ribs. (Gould 1. c.) 
**) Alcadia differs in having a slit in front of the mouth, into which 
is fitted the tooth-like process of the operculum. (Gray 1. c.) 
***) Helicinae which have a notch in the aperture. A distinction which 
it is impossible to maintain. (Sow. 1. c.) 
