OF SOUTHERN INDIA. 133 
not of a Buccimum, oreven Phos ; and the same applies to the form of the operculum. 
Hindsia, or Nassaria, as stated by Adams, forms a small group of very character- 
istic shells, to which, however, species as Canth. biliratus, pastinaca, nigricostatus, and 
a few others classed by Adams under Zritonidea (Gen. I, p. 85), ought to be added. 
On the whole, I believe that it is absolutely necessary to form a generic distinction 
for these shells, but not to separate them from the other Zrrrovizps. For the 
study of the fossil species this genus is very important; there are numerous 
shells belonging to it described from tertiary beds under Murer and Fusus, and 
some of the cretaceous species of Zritoniwm and others appear to belong also to it, as 
I shall presently mention more in detail. 
The fossil forms of the family Terronzrpx do not seem to exhibit any marked 
generic distinctions from the living, at least I am not acquainted with a single one 
which would necessitate the formation of a separate group or even a sub-genus. 
It is therefore easier to classify the recent shells, as the state of preservation 
cannot here interfere. The present difficulty in coming to a conclusive arrange- 
ment is only the want of specimens in different stages of growth, as is especially 
required in Tritoniwm and Apollon. 
The tertiary species belong mostly to Lampas, Apollon, Simplum, and a few 
eocene to Hpidromus. The number of these tertiary species is comparatively a large 
one. Of cretaceous species only a few are recorded, but the state of preservation 
scarcely allows of a very close determination. 
1.—Tritoniwm urgonense, Pict. et Camp. (Mat. p. 1. Pal. Suisse, 3me. ser., 2me. pte. 
p- 662, Pl. 96, Fig. 3, and p. 663), would appear to belong to Zritonium (as restricted). 
Pictet compares its generic identity with Zritoniwm fusiforme, Kiener, which, at 
least in its predominant characters, belongs to this genus. 
2.—Tritoniwn cretaceum, Miller (Pet. Aach. Kreidef., 1851, II, p. 47, Pl. 5, 
Fig. 2). Although Miiller (p. 48) says that the species occurs ‘in best preservation’ 
in the ‘Grimsand’ near Vaelsbrug, the representation which he gives certainly does 
not appear to be that of a perfectly preserved specimen. In no other genus, save 
LEpidromus, do the varices appear so oblique as to cross the other transverse ribs, 
and the species if perfect can therefore only belong to this; otherwise any body might 
be misled to see in it only the upper portion of the shell of a species of the 4z474. 
3.—Tritonium Konincki, Binkh. (Gast. et Ceph. Limbourg, 1861, I, p. 4, Pl. 1, 
Fig. 10) has externally the varices not well distinguished, and from the impressions 
of teeth on the inner margin of the outer lip it would appear to be a Zritonium. 
4.—Tritonium Gosawicum, Zekeli, 1852 (vide Sitz. Akad. Wien, 1865, LIT, 
Revs. ete. p. 80, Pl. 1, Fig. 4), isa Simplum, known from the aperture in good presery- 
ation. 
5-8.—Tritoniwm Hornii, Diegoensis, Alii det and Whitneyi have been 
described by Gabb from the cretaceous beds of California (Pal. 1864, I, pp. 94—96). 
None of the species was found with the aperture well preserved ; the three first named 
would seem to be Zritoniwm proper, although the shells in general very much 
resemble some species of Letodomus, Swainson, which with Adinus of Adams are 
2 
