CERITHIUM. 147 
lines in the base, though very strong, are not granulated. Specimens showing 
the full character of the aperture are not available. 
Relations and Distribution.—Differs from C. vetustwm and its varieties in a less 
marked tendency to longitudinal ornament, ¢.e. that coste, as a rule, do not 
predominate over the spiral ornamentation. Nevertheless I am scarcely prepared 
to say that these forms do not inosculate. The Yorkshire beds contain C. muricatum, 
more especially the lower portions of the Dogger proper. The variety named 
trilineatwm is almost worthy of being regarded as a distinct species (fig. 3). This 
is a unique specimen from the Scarborough Limestone. 
64, Ceriruium Gemmatom, Morris and Lycett, 1853. Plate VIII, fig. 4. 
1858. CrrirHruM G@emMMatuM, Morris and Lycett. Great Ool. Moll., p. 11 
pl. xv, fig. 6. 
1884. — _— — Hudleston, Geol. Mag., dee. 
iii, vol. i, p. 58, pl. ili, fig. 9. 
Bibliography, §¢—The type was from the Scarborough Limestone. The 
specimen now figured is from the Bean collection. 
Description.—Length 15 mm., width 4°5 mm., spiral angle 20°. Shell turrited ; 
whorls about ten, rather convex, encircled with five rows of nodules; nodules 
ovate, twenty-four in a whorl; the rows of nodules are shghtly curved ; they are 
oval, their longer diameter being in the axis of the shell, and they are distant from 
each other about their own diameter. The body-whorl shows five rows of nodules 
on the side; the base is ornamented with spiral bands, the granules of which are 
drawn out spirally, and less deeply cut. Other indications wanting. 
Relations and Distribution.—Differs from C. muricatum in the fact that the 
granules are drawn out axially rather than spirally. The beaded character of the 
granulations may be partly the result of mineralization. It occurs in the grey 
marly Oolite of White Nab (Scarborough Limestone Series), and appears to be a 
local form. It may have some relationship to Cerithiwm vetustwm, inasmuch as 
there is a tendency to axial rather than to spiral ornamentation. 
The Vetustwm-Subgroup, partly included wnder Chemnitzia by some authors. 
This group may to a certain extent be said to inosculate with the muricatwm- 
group, but its ramifications in the Inferior Oolite are much more extensive. 
