CERITHIUM. LT} 
though not very strongly marked. Fine spiral lines, somewhat wide apart, may 
be traced in well-preserved specimens. 
Body-whorl scarcely one-third the entire length of the shell, almost smooth; 
aperture subovate? Whorls ovate in section. Other indications wanting. 
Relations and Distribution.—This is a modified form of the “ gradate ” Cerithia ; 
but how far these modifications are due to mineralization it is not easy to tell. 
Until we can gauge the measure of this element of uncertainty close comparisons 
are out of the question. Rare in the Clypeus-grit of Rodborough and in the 
Parkinsoni-zone of Aston. 
The Abbas-Group. 
One other group, provisionally referred to Cerithium, yet remains, consisting of 
elongate shells of considerable size, with closely fitting whorls spirally ornamented 
(or smooth), and ovate in section. The aperture is ovate-elongate, with a long 
anterior canal, more or less reflexed. The type of the group is Cerithiwm abbas. 
It is possible that some shells heretofore referred to Fibula may belong here. It 
may be regarded as a Nerinzoid group. 
100. CeRrrHiuM ATTRITUM, sp. nov. Plate X, figs. 9 a, 9 b. 
Description : 
Length of a full-sized specimen : . 48 mm. 
Width of same : : . 12mm. 
Length of body-whorl to entire shell : . 28°: 100. 
Spiral angle S pallsxce 
Shell elongate, scarcely turrited ; spire ‘al angle vopnlan Whorls about sixteen, 
flat in the posterior part of the spire, subtumid in the anterior portion. The width 
of a whorl is equal to its height plus the height of the preceding whorl. Slight 
traces of spiral lines or belts are noticeable in the earlier whorls, but not so in the 
later ones, which are smooth and subconvex. 
Body-whorl relatively short, smooth, and subtumid. Aperture ! ? ovate, with a 
long anterior canal considerably reflexed. Whorls in section squarishly ovate. 
Relations and Distribution—The evidently rolled condition of all available 
specimens makes me rather cautious about instituting comparisons based on the 
It clearly belongs to what I have ventured to 
external appearance of the shell. 
Cerithium multivolutum, Piette (* Bull. Soe. 
call the Nerinzoid group of Cerithia. 
1 The canal is included in this measurement. 
