356 CRETACEOUS GASTROPODA 
to the smooth species only and the latter to the ribbed ones, but when large sevies 
of the same species, as, for instance, of 7. argyrostoma are compared, it will be 
seen that in some localities all the specimens are spirally ribbed, while in others 
they are less so, and again in others they are almost smooth. According to the 
degree of these spiral ribbings, the anterior margin of the aperture is more 
or less produced into a distinct lobe; this one again is channelled im young 
specimens, solid and flat in old ones, the former having at the same time the 
columella distinctly hollowed out, the latter covered with the callosity of the 
inner lip. 
2. armaticus, Gray, 1840 (ibid. p. 393). 
2a. Ocana, Adams, 1862 (Proc. Zool. Soe., Lond., p. 143), proposed for 
S. helicinus, Born, as a type. 
3. Marmarostoma, Swains., 1840 (Lunella, Bolt., in H. and A. Adams’ Gen. 
I, p. 398). 
4. Modelia, Gray, 1850 (ibid. p. 394). 
5. Prisogaster, Mérch, 1850 (ibid. p. 395) ought probably not to be generically 
distinguished from Turbo. 
6. Callopoma, Gray, 1850 (ibid. p. 395). 
7. Ninella, Gray, 1850 (ibid. p. 396). 
8. Collonia, Gray, 1852 (ibid. p. 396). 
The number of fossil species described under the name of Turbo is very large, 
but I do not think that more than one-half of them really belong to this sub-family. 
When speaking of the Zrrrorrvip# 1 have already remarked that -several of the 
fossil species of Zarbo appear to belong to Amberleya, and one or two have to be 
considered as the types of new genera. The large species of zvreryrv~ do not 
appear to have been formerly so numerous as they are at the present; they are, 
however, found represented already in the paleeozoic formations. Smaller species 
resembling the recent Collonia are very common in all secondary deposits ; they are, 
however, difficultly distinguished from similar rrocuiv%, because the opereula are 
extremely rarely preserved. 
No generic classification of the cretaceous rvrarwry has as yet been attempted, 
and I do not think that such an attempt would be followed by any success, if con- 
clusions be derived only from the descriptions and figures. The most careful 
examination of the original specimens and their comparison with recent generic 
type-specimens will be the only way to insure certainty as to the correctness of 
the determination. There can be little doubt that most of the genera, as above 
quoted, are found represented already in cretaceous beds. I may mention species 
like Turbo Jaccardi; Pict. and Camp., 7. Villersensis and Urgonensis ; T. Thur- 
manni, P. and C., and 7. Rouyanus, D’Orb.; T. Brunneri and T. Coquandi, P. and 
C., and others which successively belong to Turbo, (Senectus), Sarmaticus, Callopoma, 
Collonia, and others. We have no species of rurervzv# to report from South India, 
which seems rather remarkable, as several of the recent species are very common 
in these seas. 
