CERITHIUM. 169 
Body-whorl small relatively to the spire; aperture ? subovate, with a good-sized 
anterior canal. 
Relations and Distribution—The more slender spire, its less strongly tabulate 
character, and the continuity of the coste without bifurcation, separate this 
species from other members of the comma-group. French specimens of C. circe 
are certainly more tabulate than the one figured, which is from the Inferior Oolite 
of Dorsetshire, and is the only one of the kind known to me as British. 
The above constitute the comma-group as far as it is known to occur for 
certain in our Inferior Oolite. Thus restricted, it would be seen to be confined to 
the Upper Division. 
96. CERITHIUM (species or variety). Plate X, fig. 5. 
A Cerithium, apparently belonging to the comma-group, occurs very rarely in 
the Lincolnshire Limestone at Weldon. It is about 15 mm. long, extremely 
tabulate, and with concave whorls. The costz are numerous, short, and confined 
to the posterior margin. But these conditions are not altogether reliable, owing 
to peculiarities of mineralization. 
The body-whorl is angular, concave, and bicarinate; base rather depressed ; 
aperture subquadrate, with a well-developed anterior canal. 
The whorls are more concave than in C. comma, and the bicarination of the 
body-whorl is another marked feature of difference. As a temporary name we 
may distinguish this as Cerithium commaoides. 
In some respects also this form leads up to a group of Cerithia with tabulate 
whorls and no axial ornamentation. 
97. CERITHIUM PERGRADATUM, sp. noy. Plate X, fig. 6. 
Description : 
Length . : 5 ; . 20 mm. 
Width : , : : . 625 mm. 
Spiral angle : i 5, Ss 
Shell subelongate, conical, strongly turrited ; apical conditions unknown. 
Whorls about twelve in number, flat or slightly excavated anteriorly, and increasing 
by steps so as to overlap the suture, which is channeled. A raised rim marks the 
posterior margin, which is spirally striated; plain spiral lines succeed, which are 
about six in number in the anterior whorls. 
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