174 GASTEROPODA OF THE INFERIOR OOLITE. 
The body-whorl is similarly ornamented, and is slightly angular ; base full and 
striated spirally with a very fine pattern, which slightly decussates with axial 
lines. Aperture ovate-elongate; columella straight and but little encrusted ; 
anterior canal produced. 
Relations and Distribution —Related to Cerithium abbas, var. C, this species is 
still more like a Nerinxa. A single specimen from the Sauzei-bed at Oborne. 
Genus—Fisuna, Piette, 1857. *‘ Bull. Soc. Géol. France,’ 2™° sér., vol. xiv, p. 556. 
The characters of this genus are not particularly well defined. Piette regarded 
it as something between a Twurvritella and a Cerithium. Lycett (‘ Suppl.,’ p. 16) 
gives the following modified diagnosis: “A rounded, straight columella, with a 
rudimentary umbilical groove near the base, is combined with an arcuated outer 
lip, slightly notched posteriorly at the suture; the base of the aperture forms a 
slight canal at its junction with the anterior extremity of the columella, or in other 
instances there is no canal. . . . . The surface of the volutions is plain or 
slightly ornamented with oblique coste.’’ Piette’s types were Fibula undulosa 
and F’, nudiformis, to which Lycett added Fibula variata, Lyc., F. eulimoides, 
Whiteaves, and I’. phasianoides, M. and L. All five are Great-Oolite species, 
M. Cossmann (‘L’Htage Bathonien,’ p. 108, e¢ seg.) more or less does away 
with Fibula by merging it in Ceritella, so that, according to this arrangement, 
F. undulosa, P., and F. nudiformis, P., become Ceritellx.' Fischer regards Fibula 
as a subgenus of Ceritella. Whether Fibula is worth preserving as a genus or not 
it is eminently a Bathonian group; so also is Ceritella. Both are extremely rare in 
the Inferior Oolite of England. The two species which I now propose to classify 
under Fibula might possibly be allowed a place under Cerithium. The species in 
the Inferior Oolite which I regard as belonging to Ceritella have the body-whorl 
relatively longer and more approaching the cylindrical form. 
104, FIBULA ANGUSTIVOLUTA, sp. nov. Plate XI, fig. 1. 
Description : 
Length . : ; : - 12mm. 
Width 3 ; é 5 aration, 
Ratio of body-whorl to entire shell ‘ ~ S000: 
Spiral angle ; , : . 25°. 
1 Fibula Royssii, d’Arch., comes under another category. 
