104 UNIVALVES. TROCHUS. 



Of these species there are two distinct varieties: one is 

 called the Conchologist, from its being loaded with frag- 

 ments of shells, and other testacjeous substances; and the 

 other is very properly named the Mineralogist, as its bur- 

 then consists of stones, earths, pebbles, ores, &c. When 

 the former 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 Trochiare much elongated, and great- 

 ly 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 T. telescopium and T. dolabratus. 



The greater part of the Trochi present a brilliant mo- 

 ther-of-pearl appearance when uncoated; others have 

 only their aperture pearly or silvery; and a few exhibit 

 a bronze-like hue. 



There are several reverse varieties of Trochi: the prin- 

 cipal are— T, perversus, T. undulatus, T. ventricosus, T. 

 annulatus, and T, pusillus; the latter of which is found 

 within larger shells, in the sands of India. 



The T. flumineus is a river species, and theT. horten- 

 sis is an inhabitant of the gardens in warmer climates. 

 The T. terrestris is also a land species, and frequents the 

 mountains of Cumberland. 



Amongst the fossil species, there are two with the 

 whirls contrary, viz. T. ferrugineus and T. noyus: the 

 former of which is found near Staphusia, converted into 

 iron-ore. The T. Schrceteri is also found fossil in Cam- 

 pania. 



. The following are the places which yield specimens of 

 the Trochi: viz. Asia, Africa, America, Friendly Isles, 

 New Zealand, Red Sea, Mediterranean, the European 

 and British seas, &c, 



