CLASSIFICATION. 1 7 



bisexual, and so largely mentioned hereafter, that extended 

 analytic remarks are not required. We will only point out 

 the curious fact that all the Pyramidellidce 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 011 the 

 succeeding volution : these two points will invariably detect the 

 Chemnitziau 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. Chemnitsia, though a proboscidal 

 animal, seems to have some alliance with the amphibious 

 pulmoniferous Conovuli and the land Carychium. 



Though the family of the Cerithiadce, 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 tuber cularis. 

 It has been stated that the muzzle of C. reticulatum differs 

 from that organ in the Littorince and Rissoce ; 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 Cerithiadce, it will be seen that it has 

 little alliance with it, for we shall prove, in our family of the 

 Alatidce, 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 Cerithiadce, 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. 



