404 ] HELICINA $. 12. 
miovalis; columella brevis, basi subtuberculata, superne linea 
impressa, transversa marginata; perist. subincrassatum, album, 
reflexiusculum, margine supero sinuoso. — Operc.? — Diam. 
m23]..:9, min. 8;.-alt.. 7 mall; (Coll, NE: 
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 I. variabili et Columbianae, huic statura et forma 
similior. 
705 148. Hf. troehlea Gould. 
T. minuta, trochiformis, supra cinerea, cosüs acutis vol- 
ventibus 3 vel 4 (intervallis concavis, scabrosis) cincta, infra 
convexa, polita, citrina; spirae anfr. 4, ultimus ad peripheriam 
biearinatus; apertura subtrigona; perist. leviter reflexum ; 
columella ad basim angulata, callo copioso induta. — Tat. 
ali 9, poll.:66) 
Helicina trochiea 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. "esta heliciformis, turbinatai 
subglobosa vel depressiuscula, plerumque pilosa, basi circa 
columellam subplanulatam ,  strictiuseulam — eallosa; apertura 
triangulari-semiovalis; peristoma magis minusve expansum, 
incisura distincta, plerumque curvata, a columella sejunctum. 
"Aicadia Gray 1840. Syn. Brit. Mus. p. 134. Ed. 1842. p. 91. **) 
— . Gray in Proc. Zool. Soc. 1847. p. 182. n. 533. 
— Som. Conch. Man. ed. II. p. 61. ***) 
*) It has the size and nearly the form of 4. rupestris Pfr., and is 
distinct from all others by its well-marked, sharp, revolving ribs. (Gould l. c.) 
**) 4icadia differs in having a slit in front of the mouth, into which 
is fitted the tooth-like process of the operculum. (Gray l. c.) 
***) Helieinae which have a notch in the aperture. A distinction which 
it is impossible to maintain. (Sow. l. c.) 
