95 
TROCHUS similus. 
TAB. CXLII. 
‘Spec. Cuar. Conical, base rather convex, volu- 
tions squarish, with tubercles upon their angles, 
transversely carinato-striate, and a round- 
ing elevation in their centers ; lines of growth 
decussating the three central striz. 
SS ae 
"Tue tubercles are numerous, rather depressed, but 
large, the stria are undulated and pass over them ; be- 
tween the three central strie which lie upon the elevated 
part of the whorls the lines of growth are seen very 
sharp, close and regularly arched: the columella is im- 
perforate, and the interior of the shell is nearly plain, 
retaining but small signs of the tubercles: the aperture 
is square with rounded angles, and the inner lip is thick- 
ened, two characters not well expressed in the figure, 
which was taken from a handsome, but in this respect an 
imperfect specimen. 
The Blue Lias at Weston near Bath, and in the neigh- 
bourhood of Yeovil, Lackington Park, Shotover, &c. 
abounds with this Trochus. Lister found it at Bugthorp, 
Yorkshire, and has figured it in his Conchology, f. 1036. 
It is found of considerable size, and more or less worn 
so as to disguise it in a way that makes it often difficult 
to distinguish the species. When most perfect it is very 
much ornamented with transverse undulating strie, and 
often a rather conspicuous sort of belt, which has what 
some have occasionally denominated a herring bone 
marking. Among my specimens are several casts of the 
interior only ; some are included in a mould of the outer 
surface, like the lower figure; and the space between 
