148 GASTEROPODA OF THE INFERIOR OOLITE. 
The numerous varieties and species which I refer to the vefwstwm-group 
have a tendency to longitudinal ornament, and even when their ornaments 
are markedly granular, the granules are usually drawn out axially rather 
than spirally. Cerithium flecwosum, Miinst., as it seems to me, represents the 
immature condition of some varieties, where arcuate longitudinal coste prevail 
before any turriting has commenced, whilst C. muricato-costatum represents 
robust varieties, where the granules have been more or less fused into continuous 
longitudinal coste. This tendency to longitudinal ornamentation, so conspicuous 
in corroded specimens, has caused the original Terebra vetusta of Phillips to be 
classed under ‘‘ Chemnitzia” even by D’Orbigny, although the representative 
species in the Bajocian of Normandy (Nos. 172 and 188 of the 10th stage) are 
classed under Cerithiwm in the ‘ Prodrome.’ 
As regards nomenclature, the difficulties which beset all demoid forms are 
aggravated in this case. Firstly, the prior name was given to a corroded specimen 
of the stunted species which occurs in the Millepore- and Scarborough-Limestone. 
Secondly, the whole group is peculiarly liable to have its ornaments affected by 
variations in conditions of mineralization, and this is particularly the case in the 
beds whence the type was derived. Miinster’s names, though very useful, and no 
doubt applicable to the German beds, represent conditions of mineralization, and 
in the case of C. fleruosum (only 10 mm. in length) even a stage of growth in all 
probability. Without in any way asserting, that the method adopted in this Mono- 
graph for dealing with such an extensive group is the best, it possesses the merit 
of exhibiting the facts of the case as they occur in the Inferior Oolite of this 
country. Some dubious forms, presumably belonging to this group, have not been 
noticed, but Miinster’s names would cover the majority of them. 
65. CErituium vetustum, Phillips, 1829. Plate VIII, figs. 5 a, 5 b, 5 ¢, 5 d. 
1829. TerEpRa verusta, Phil. Geol. York., Pt. I, vol. i, p. 152, pl. ix, fig. 27. 
1844, CrrrrHiuM MURICATO-cosTatUM, Miinst. Goldfuss, t. 173, fig. 12. 
1844. — GRANULATO-costaTUM, Miinst. Goldfuss, t. 173, fig. 10. 
1844. —  ?rnexvosum, Miinst. Goldfuss, t. 173, fig. 15. 
1850. Curmntrzta verusta, D’Orb. (Phil.). Prod., vol. i, p. 268. 
1851. — Pp — Phil. Morris and Lycett, p. 114, pl. xv, fig. 7. 
1869. Crrrraium verustum, Williamson. Brauns, Mittl. Jura, p. 172. 
1882. “Cnemnirzia” verusta, Phil. Hudleston, Geol. Mag., dee. ii, vol. ix, 
p- 247, pl. vi, figs. 9—11. 
Bibliography, Sce.—Brauns, in sweeping up the muricato- and granulato- 
costate Cerithia of North-west Germany into this net, included Cerithiwm armatum, 
