CERITHIUM. / 161 
83. CERITHIUM LIMmroRME, Romer, 1836, var. Pontonis{ sp. nov; Plate IX, fig. 7. 
1836. CERITHIUM LIMHFoRME, Rim. Ool. Geb.,, tab. xi, fig. 19, p. 142. 
Bibliography, 5e.—Romer’s species was originally described and figured from 
the Coral Rag of Hoheneggelsen. Morris and Lycett referred to CO. limeforme 
and to C. quadricinetum, Miinst., a similar group of shells occurring in the Great 
Oolite of Minchinhampton. Subsequently Lycett (‘ Suppl.,’ p. 122) observed that 
what the authors of the ‘ Great Oolite Mollusca’ had regarded as two separate 
forms must be united into one species,. and to this he assigned the name of 
C. quadricinctum, Miinst. The figure in Goldfuss is not very like either the 
Ponton or the Minchinhamptom fossils. On the other hand, there cannot be any 
doubt that the Ponton shells are closely related to C. limxforme, Rém., a name 
which in a certain sense is applicable to the entire group now under consi- 
deration. 
Description : 
Length : : ; . 10 mm. 
Width : : ‘ . 3s mm. 
Length of body-whorl to entire shell, about = oon lOO: 
Shell small, subelongate, scarcely turrited; spiral angle very convex. The 
apex is blunt; number of whorls about ten, flattish; suture rather open. The 
subapical whorls exhibit two to three tuberculated spirals, and the tubercles on the 
two upper rows have a tendency to coalesce axially so as to produce coste. In the 
anterior whorls the two upper spirals are strongly tuberculate, and have the effect 
of producing a kind of zone. The number of spirals varies, but is three or four. 
In some cases where there are four the third is faint, as in C. Beanit. 
The body-whorl is about one-third the length of the entire shell, and similarly 
ornamented with spiral lines on the base. Aperture sub-oblong, with a broad, 
short anterior canal. 
Relations and Distribution.—This particular variety of the limeforme-group is 
distinguished by its slender shape and somewhat more delicate ornamentation 
both from C. Beanii on the one hand, and from C. Wansfordix on the other. It 
is the prevailing form at Ponton, but met with sparingly elsewhere in the 
Lincolnshire Limestone. The Minchinhampton forms, referred by Lycett to 
C. quadricinatum, Miinst., are on the whole more slender, less markedly pupoid, 
and finer in their ornamentation. Although the bulk of the specimens of 
C. Pontonis are more irregular in ornamentation, and have a slight tendency to 
the cingulate arrangement, there are specimens from Ponton which can in no way 
be distinguished from specimens of C. limexforme occurring in the type locality of 
Hoheneggelsen. 
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