CLASSIFICATION. 17 
bisexual, and so largely mentioned hereafter, that extended 
analytic remarks are not required. We will only pomt out 
the curious fact that all the Pyramidellide have the eyes 
immersed at the internal bases of the tentacula, and the apex 
of the shell is, I believe, always more or less reflexed on the 
succeeding volution : these two points will invariably detect the 
Chemnitzian animal; the tooth also is of excellent value when 
present, but as the shell is as often without as with it, it 
is not always available. Chemnitzia, though a proboscidal 
animal, seems to have some alliance with the amphibious 
pulmoniferous Conovuli and the land Carychium. 
Though the family of the Cerithiade, with its genera Cerithium 
and Aporrhais, in which some British species are deposited 
by authors, has no place in our method, it is proper to make 
a few remarks on it. We propose hereafter to show that the 
Cerithium reticulatum of authors is an elongated Rissoa, and 
that the C. adversum, from its spiral operculum, is also a 
probable Rissoa: we think C. metula, a Cerithiopsis with some, 
is an elongated Murex, ranging with our Murex tubercularis. 
It has been stated that the muzzle of C. reticulatum differs 
from that organ in the Littorine and Rissoe; I am unable to 
discover a tangible difference, and think that the animals are 
in every respect the prototype of each other. 
As for the Aporrhais pes pelecani, which has sometimes 
found its way into the Cerithiade, it will be seen that it has 
little alliance with it, for we shall prove, in our family of the 
Alatide, one of Lamarck’s groups, to which it is transferred 
as Rostellaria pes pelecani, that it is a nearly strict muricidal 
animal. 
We think the family of the Cerithiade, even as regards 
exotics, is altogether conchological and artificial; it is pro- 
bable many of its animals will turn out simple Rissoideans, 
and many, elongated Murices. 
