NON-PULMONARY GASTEROPODS. 
411 
wished -with two conical tentacles, having at their base eyes borne on 
a peduncle ; its foot is short, round at its two extremities, edged or 
fringed in its circumference, and furnished with a horny operculum, 
C1 i'cular and regularly spiral. 
The family is divided into many sub-genera. Among the Tro- 
oho'idx, properly so called, we may notice a typical species, Trochus 
n 'ihticus (Fig. 211) and Trochus virgatus (Fig. 212). The Zedaria 
c °mprehend the false-sided Trochoidse, typical of which we may notice 
Trochus inermis (Fig. 213), whose greenish-yellow shell -is found in 
Fig. 213. Trochus inermis (Gmel.). Fig. 214. Trochus Cookli (Chemnitz). 
ffie American seas; Trochus CooUi (Fig. 214), whose rusty-brown 
a hell is brought from the distant seas of Australia ; and Trochus 
inilricatus (Fm 215), whose white-coloured shell comes from the 
Antillps. 
Fig. 215 . Trochus imbricatus (Gmel.). Fig. 216. Trochns agglutinans (Lamarck) ; 
Phorus couchyliophorus (Bom). 
Another remarkable species, the Phorus couchyliophorus (Born), 
^ochus agglutinans (Lamarck), is a native of the Antilles, popularly 
known as the Mason (Figs. 216 and 217), from the singular faculty 
11 has of collecting on the back of its shell, in proportion as they 
