UNIVALVES. TROCHUS. 113 



TROCHUS TOP-SHELL. 



slnimat a Limax: Shell univalve, spiral, more or less co- 

 nic; aperture somewhat angular or rounded, the upper 

 side transverse and contracted; pillar placed obliquely. 

 THIS genus contains one hundred and twenty-nine spe- 

 cies. The leading characteristic consists in its conical 

 shape, which prevails with few exceptions throughout the 

 genus ; some, however, are so nearly allied to the Turbo, 

 that frequent mistakes arise in their classification. 



Among those Trochi which have their pillar perforated 

 or umbilicated, may be mentioned the T. Niloticus, T. ma- 

 culatus, T. perspectivus, T. hybridus, and T. Pharaonis. 



Though some of this genus have their surfaces almost 

 smooth, yet the greater number are covered with knobs, 

 spines, tuberculations, or undulations, of which the T. so- 

 laris and T. imperialis, are striking examples : the former 

 has its margin beset with long spines, placed at regular 

 distances, resembling, when the shell is perfect, the rays 

 of the sun as represented in carved work : it has also a 

 most beautiful gold colour, which occasionally shines forth 

 through the ochreous surface of the shell, and of course 

 adds materially to the similitude. The T. imperialis is 

 generally of a dull olive colour, but there is a rare variety 

 of it which has a pinkish cast, and is known by the name 

 of the Pink Sun : they are both from the South seas. 



Of the imperforated species, the most characteristic are 

 the T. vestiarius, T. labeo, and T. tuber ; the latter of 

 which very much resembles a Turbo. 



The T. iris, when uncoated, is celebrated for the splen- 

 did metallic lustre which illumines its surface, and for the 



