186 
TROCH U S. TOP-SHELL. 
The rounded outline of the front margin, the want of the 
ear-shaped appendages, the internal rib, and more espe¬ 
cially the accessorial dorsal valves, strongly mark this spe¬ 
cies from the two last. It may also be observed that the 
hinder part is closed when the valves are placed together* 
ill consequence of their rounded outline. 
Thrown up on the Devonshire coast, v. m. 
TROCHUS. TOP+SHELL. 
Shell with a single valve, spiral, more or less 
conic: aperture somewhat angular or rounded, 
and contracted transversely : pillar placed ob¬ 
liquely. 
A. Perforated at the base, 1 to 5. 
B. Impelforate at the base , 6 to 11. 
# 1. Trochus Magus. Tub cycled Top-shell. Fig. 64. 
Lister , pi. 641. f. 32 — Pennant , pi. 83. f. 4— Da Coda * 
pi. 3. f. 1— Donovan , pi. 8. f. 1— Dorset Cat. pi. 16. f. 1,2. 
Shell with five or six tumid spires, a little depressed, 
ending in a fine point, marked with fine circular ridges, 
well defined by a deep separating line, and a raised rib 
round the base of each; the top of each volution rather 
flattened, and surrounded with a row of obtuse tubercles 
or short ribs seated close to the ridges, and most conspi¬ 
cuous on the larger ones : color dull white or brownish, 
often marked with irregular spots lines or undulutions of 
scarlet, pink, pale purple, or ehesnut-brown: aperture u 
little compressed and somewhat angular, the pillar a little 
prominent in the middle, with a large and deep perfo¬ 
ration. When the outer coat is removed it presents the 
richest iridescent perlaceous hue : diameter from an inch 
to an inch and a half, and about as much in height. 
On most sandy shores, v. v. 
2. Trochus umbilicatus. Purple-tipped Top-shell. 
Pennant , pi. 83. f. 3— Da Costa, pi. 3. f. 4— Donovan , 
pi. 74, middle fig.— Dorset Cat. pi. 16. f. 7, 8. 
Shell Ayith five spires, which are hardly raised or distinct 
