150 GASTEROPODA OF THE INFERIOR OOLITE. 
Limestone series (Pickering Cliff, &c). It is doubtfully quoted from the Lincoln- 
shire Limestone in Judd’s ‘ Geology of Rutland.’ Specimens from the Cotteswolds 
may be referred to C. vetustwm or to C. granulato-costatwm according to condition. 
66. Crriraium verustum-maJus, Hudleston, 1882. Plate VIII, figs. 6a, 6b. 
1882. ‘ Cremnirzta” verusta-MAJoR, Hudl. Geol. Mag., dec. ii, vol. ix, p. 248, 
pl. vi, fig. 12. 
Description : 
Length (large size). ; : . 43 mm. 
Width ‘ : : : . 10mm. 
Spiral angle : ; F ates 
Shell elongate, turrited; whorls flat to subconvex, and only turrited 
anteriorly ; about twelve in number; suture distinct. Strong longitudinal ribs, 
having a crescentic curve, characterise the spine. ‘The precise apical conditions 
are unknown. The anterior whorls have the longitudinal ribbing decussated by 
about six spirals, producing nodes at the points of intersection. In the larger 
specimens the last two whorls have the longitudinal ribbing less strongly marked, 
whilst the spiral ribbing towards the posterior margin becomes more pronounced, 
presenting somewhat the appearance of a nodular varix, which much increases 
the turrited aspect of the shell. 
The base is strongly ribbed spirally. The aperture is somewhat widely ovate ; 
and some specimens give evidence of a tolerably long anterior canal, but slightly 
reflexed. 
Relations and Distribution.—It is by no means improbable that Cerithium 
jlecuosum, Miinst., represents the apical conditions of this species. It is closely 
allied to the larger varieties of Melania undulata, Deslong., whilst the typical 
Cerithium vetustum of the Scarborough Limestone, &c., is its attenuated repre- 
sentative on a higher horizon. 
In Yorkshire the larger shells are confined for the most part to the principal 
shell-bed of the Dogger, but it is seldom that the ornaments are in a good state of 
preservation. In some of the other parts of the Doggér these are better pre- 
served, but on the whole smaller. 
