OF MOLLUSCA. 147 



pearance. The periphery is ornamented with radiating horny fibres. 

 —Adams, P. Z. S. 1850, p. 50. t. 8. f. 21. 



2. Lippistes. 

 Shell subdiscoidal ; mouth round ; lips scarcely reflexed. 



1. L. cancellata. Cyclostrema c, Leach. 



2. L. evoluta. Delph. e., Reeve. 



b. Body and whorls compressed, subquadrate, flattened in front. 



3. Adeorbts. 



Shell suborbicular, white, umbilicated ; whorls spirally ribbed ; 

 aperture subquadrate, ovate, very oblique. Peristome continuous, 

 simple ; throat pearly. Operculum orbicular, shelly, circular, flat, 

 closely multispiral, with a frosted surface. 



1. A. subcarinatus. Trochus s., Montague. 



Fig. 80. — Operculum 

 Fam. V. TROCHHLE. of Trochus. 



Operculum horny, of many gradually enlarging 

 whorls, not covered with a calcareous coat (fig. 80). 

 No frontal fringe between the tentacula. Rostrum 

 produced. 



A. Operculum circular, many -whor led (fig. 80) (p. 158). 



a. Shell top-shaped; aperture of shell contracted, quadrangular; 

 whorls compressed, subquadrate, flat in front. Trochina. 

 (Page 155.) 



§ Axis of shell imperforated, slightly concave in front. 

 1. Pyramis. 



Shell conical, imperforated, flat in front; aperture subquadran- 

 gular, wider than long ; pillar short, spirally twisted, and acute in 

 front. 



1. P. obeliscus, t. 39. f. 3. 



2. Cardinalia. 



Shell conical, imperforated, flat in front ; aperture four-sided ; 

 pillar-lip simple above, without any groove, and ending in a simple 

 point in front. 



1. C. elata, t. 61. f. 22, 26. 



l2 



