OF SOUTHERN INDIA. 27 
All these three forms are generally ornamented with transverse ribs. 
4th.—Species with slightly dilated wing, soon dividing into two or three long 
extremities, carinated and usually spirally striated whorls et cet.—as the 
long known Al. myurus, Desh. or Al. levigata, Morris, might be referred 
to Tessarolax, Gabb.* i 
5th.—To retain under Aporrhais only those species, which have a broad dilated 
wing from the base, terminating exteriorly in as many points, as there are 
keels on the exterior side of the wing, which ought in all cases to extend 
to the exterior margin of the wing, asin Ap. Dupiniana, D’Orb. or Ap. 
(Chenopus) atractoides, Desh. 
6¢h.—The Jurassic Diarthema paradoxa, Desh. forms a separate genus, somewhat 
allied to Ranella. 
7th.—Spinigera of D’Orbigny ought probably to be classed here better than 
with Ranella. 
The genus Hustoma, Piette, will be mentioned hereafter in the Cerrrurrpz; its 
position is at present uncertain. 
Through a limitation of Aporrhais in this way we evidently come into Plerocera 
and Strombus, when such a review becomes nearly exhausted, and would again sug- 
gest considerable alterations. 
IT have already stated, that it is not through the living species of Strombus and 
Pterocera, that these great obstacles are produced, but through the large number 
of the fossil so-called Péerocera, which give so little hope of an early and suc- 
cessful classification. The difficulties, however, become insurmountable, should 
such an unnecessary separation be acknowledged, as has been proposed by the 
creation of the families dporrwarpx and S‘rrouzrpxz. The length of the canal or 
mantle-fold cannot form a very important distinction, for the canal is quite as short 
in many true S7rouerpz, as it isin Aporrhais or Struthiolaria. The form of the 
rostrum in the animals of the two last named genera is no doubt quite similar 
to that of many Crrrruipsz, but the different genera of this family show also 
a similarly considerable variation in the form of this organ (see Vertagus, Ceri- 
thium, Telescopium, Triphoris and Cerithidea), if perhaps not to the same extent, 
as the Azara. H. and A. Adams state, (loc. cit. p. 281) that especially the fossil 
forms indicate strong affinities of Aporrhais with Oerithium; I confess, that I am 
not aware of any fossil forms such as would support a separation of this kind. 
Where affinities have been pronounced as existing between the two genera, it 
was, and still remains to a great extent, to be shewn, whether these had not arisen 
merely from the incompleteness of the fossil species of the dAzara, Many of 
the older secondary species of Czrrrurrpx exhibit great relations to some species 
of the Trocuipm and many Chemnitzie, but they cannot be generally mistaken 
for Aporrhais or other allied genera. 
* Palexont. of California, 1864, I, 126, Pl. 20, Fig. 82. 
