458 PHILOSOPHY OF ZOOLOGY. 



is similar to the snails. While the shells of the helix are 

 globose, those of bulimus are turreted. 



2. Last Whorl nearly of the same size as the penultimate 

 one, or even less. 



The species which are related to the Turbo b'idens per- 

 versus and muscorum of LINNAEUS, constitute a very natu- 

 ral family, which may be termed PUPAD.E, distinguished 

 by the mouth being, in general, furnished with teeth, or 

 testaceous laminae, and the last whorl nearly the same 

 as the preceding. Perhaps the most convenient way of 

 dividing them is into two sections, the first ^including the 

 dextral, and the second the sinistral shells. 



The dextral pupada form three genera. The PUPAJ as 

 originally constructed by LAM ARK, was equally faulty with 

 many of the old Linnaean genera. As we have restricted 

 it to include dextral shells, with the animal possessing four 

 tentacula, with eyes at the tips of the two longest, we can 

 receive into it the muscorum, sexdentatus, and juniper i of 

 MONTAGU. The genus Chondrus of CUVIER contains the 

 tridens of MONTAGU. In the genus CARYCHIUM, formed 

 by MULLER, the tentacula are only two in number, with 

 the eyes placed at the base. It is represented by the T. 

 carychium of MONTAGU. 



The sinistral pupadae form two genera. The first, 

 which is the Clausilia of DRAPARNAUD, contains sinistral 

 shells, the animal furnished with four tentacula, having 

 eyes at the tips of the two longest. To the pillar there is 

 attached internally a twisted plate. This contains the fol- 

 lowing British species, -perversa, nigricans, laminata, bi~ 

 plicata, and labiata. The other genus, called VERTIGO, was 

 formed by MULLER. The animal possesses only two ten- 

 tacula, with the eyes on their tips. The T. vertigo is the 

 type of the genus. 



