UNIVALVES— TROCHUS. 141 
TROCHUS.— Tor-Sue tt. 
DESCRIPTION OF PLATE XXVII. 
Div. I.— Fam. 1. 
Fam. 1. Fig. 1. T. solaris. 
Dy. Il.—Fam. 1. Fig. 4 T. cookii. 
; Fam. 1. Fig. 2. T. iris. 
Dw. IIl.—Fam. 1. Fig. 3. T. telescopium. 
Fig. 5. T. concavus. 
Shell univalve, spiral, more or less conic; aperture somewhat angu- 
lar or rounded; the upper side transverse and contracted; pillar 
placed obliquely. 
THE leading characteristic of the Trochus is the coni- 
cal shape of its species, the base being broad and the 
whorls gradually tapering towards the apex. This form 
prevails with very few exceptions throughout the genus; 
some, however, have so strong a resemblance to the 
Turbo, that ‘frequent mistakes have been made in their 
classification. 
A few species of this genus have their surfaces almost 
smooth; but the greater number are covered with knobs, 
spines, tuberculations, or undulations, of which the T. 
solaris and the T. imperialis are striking examples. The 
former has its margin beset with long spines, placed at 
regular distances, and, when the shell is perfect, re 
sembling the rays of the sun, as represented in carved 
work. Many, when uncoated, present a brilliant mother- 
of-pearl appearance; others have only a pearly aper- 
ture, and a few exhibit a bronze-like hue. The aper- 
