11") UNIVALVES TROCHUS. 



The operculum often varies in shape, according to the 

 form of the mouth it lias to close : in some instances it is 

 elongated, and has a horny appearance ; in others it is 

 circular, and of a very compact testaceous substance; 

 some are perfectly smooth, others strongly granulated. 



The Trochus conchyliophorus, or carrier Trochus, is 

 a very curious and remarkable species ; for it is invariably 

 covered with other substances, strongly adhering to the 

 whorls of the shell. There are two distinct varieties: one 

 of which is called the Conchologist, from its being loaded 

 with parts or fragments of shells, and other testaceous 

 substances; the second variety is very properly named 

 the mineralogist, as its burthen consists of stones, earths, 

 pebbles, ores, &c. When the foniier variety is loaded with 

 corals only, it is called the zoologist or coral-carrier. 

 They are considered, when heavily laden, as rarities. 



Some species of Trochi are much elongated, and greatly 

 resemble screw or needle shells. Unlike the rest of the 

 genus, they have an exserted pillar; and, when placed 

 on their base, they fall on one side. The most promi- 

 nent species are the Trochus telcscopunii or telescope 

 Trochus, and the Trochus dolabratus. 



The greater part of the Trochi present a brilliant mo- 

 ther-of-pearl, when uncoated; others have only their 

 aperture pearly or silvery; whereas some again are of a 

 hue something resembling bronze. 



There are several reverse vari^eties of Trochi: the 

 principal are — Trochus perversus, luidulatus, ventricosus, 

 annulatus, and pusillus; the latter of which is found 

 within larger shells, among the sands of India. 



The flumineus is a river species, and the hortensis is 

 an inhabitant of the gardens in warmer climates. The 

 terrestris is also a land species, and frequents the niouu- 

 taius of Cumberland. 



