OF SOUTHERN INDIA. 309 
while Naticodon has only one; as regard the thickness of the shell this transi- 
tion seems equally to hold good. It is possible, that some of the smooth liassic and 
jurassic species of Neritopsis, like N. levis, Stol. (Sitz. Akad., Wien, 1861, XLITI, 
-p. 179, pl. 8, fig. 6,) and others belong to Naticodon. With regard to cretaceous 
species it is very difficult to make any suggestions. I have never myself observed a 
single species with only one columellar tooth, though I am rather disposed to believe, 
that species like Neritopsis Renauxiana, D’Orb. (Pal. frang. erét. II, p. 175, pl. 176, 
figs. 5-6), and perhaps Nerit. ornata, D’Orb. (ibid. figs. 8-10,) and others may be 
rather called Naticodon than Neritopsis. 
3. Neritopsis, Grateloup, 1832 (Sowerby, 1834). Shell thick, globose, whorls 
rapidly increasing im width; last volution very large, more or less enveloping the 
previous ones; inner lip strong, callous, distinctly excavated in the middle ; columella 
generally solid; surface of shell usually cancellated or spirally ribbed. 
The great consistency of the shell, and the thickened and excavated inner lip, 
readily distinguish this genus from the two last named ones. There are only one or 
two* recent species known, and the fossil ones also do not appear to be very numer- 
ous, though they are undoubtedly more common in the older periods than in the 
more recent ones, having had their maximum in the time between the upper triassic 
and the middle jurassic periods. Pictet and Campiche (Mat. Pal. Suisse, 3me. 
Ser., pp. 408-409,) quote from cretaceous rocks fifteen European species, but of 
all those that are figured or properly diagnosed, I find that only the NV. Robineausiana 
and N. pulchella appear to be true Neritopsis; possibly also the WN. levigata, 
though this is by no means equally certain. All the remaining species described 
under the generic name Neritopsis are doubtful, though some of them may probably 
represent imperfect specimens of Neritopsis; others, however, more likely belong 
to Vanikoro, and again some of them, like N. scalaris, Seeley, or NV. costulata, 
Rémer, may possibly be shown to be species of Nerita. 
From North America, two species have been reported, Nerit. ? Tuomeyana, 
Meek and Hayden (Nat. id., Proc. Acad. Nat. Sc. Phil., 1856, p. 270; Smithson.. 
Mise. Coll. No. 177, 1864, p. 18), and Nerit. biangulatus, Shumard, Trans. Acad. 
St. Louis, 1860, p. 598. 
We have procured from Sth. India only a single fragmentary specimen, which 
we shall describe as Neritopsis crassa. 
LXIX. VANIKORO, Quoy and Gaimard, 1832. 
1. VaniKkoro munita, Forbes, sp., Pl. XXII, Fig. 16. 
1846. Nerita munita, Forbes, Trans. Geol. Soc., Lond., VII, p. 122, Pl. XII, Fig. 15. 
5 ? Natica obliquistriata, Forbes, ibid.  ,, es a Delo, bl xa ion 2: 
1850. Natica munita, D’Orbigny, Prodr. I, p. 222. 
Van. testa sub-globosa, sub-depressa, spira paulo elevata; ultimo anfractu 
multum latiore quam alto, ad basin rotundato, late excavato ; apertura semilunari, 
* I think a new species has been described from the Pacific Islands or Taheiti, but I am just now unable 
to find the reference. 
4A & 
