158 GASTEROPODA OF THE INFERIOR OOLITE. 



The body-whorl is relatively small, base rather flat. Aperture subquadrate, 

 with a straight columella. Canal apparently short, other indications wanting. 



Relations and Distribution. — This form appears to have relationship to the 

 several species described by Deslongchamps from the Inferior Oolite of Normandy, 

 as Cerithium triseriattim, quadriseriatum, &c. With these, unfortunately, I am 

 unacquainted. It is noticeable, however, that in this species we lose the compara- 

 tively strong longitudinal ornamentation of the vetustum-growp. 



Single specimen from the Inferior Oolite (? Murchisonge-zone) of Coker. 



The Limaiforme-Growp. 



This group is intended to include Ccrithia which are usually rather small, 

 often pupoid, and with fine ornaments, where the spiral lines are more 

 conspicuous than the longitudinals. The aperture has rather a tendency to 

 be subquadrate, columella short, with a short but well-developed anterior canal, 

 slightly reflexed. Judged by the character of the aperture these little shells are 

 perhaps more nearly allied to the existing genus Cerithium (including Bittium) 

 than the group last described. In the Lower Oolites of this country Cerithium 

 Beanii, and C. Umseforme are the two species round which the less common forms 

 may be grouped. But these also vary so obviously that it is almost impossible to 

 draw a very distinct line. In order to realise how hopeless it is to make " hard- 

 and-fast species " out of this group, let anyone study a well-stocked collection of 

 small Gerithia, from the Lincolnshire Limestone. And yet it is equally impossible 

 to avoid the temptation of making a certain amount of nominal differentiation. 



79. Ceeithidm Leckenbyi, Hudleston, 1884. Plate IX, fig. 4. 



1884. Cerithium Leckenbyi, Hudl. Geol. Mag., dec. iii, vol. i, p. 61, pi. iii, 



fig. 12. 



Description : 



Length (restored) . . . . ? 17 mm. 



Width . . . . .4 mm. 



Height of whorl to width . . 2 : 3*75. 



Spiral angle . • • . 14 . 



Shell elongate, subturrited ; whorls (?) thirteen, flat, short in comparison with 

 their width ; sutures close. The ornaments consist of finely granulated or 

 tuberculated spirals, of which the first is strongest and the fifth the faintest. 

 The longitudinals are irregular as in G. Beanii, frequently not reaching to the 



