PULMONATA. 79 
slightest pressure, as the animal emerges from the shell, and the clausium is then 
bent back against, and fits upon, the curved columella, but recovers its former position 
by the recoil of the pedicle on the removal of the pressure when the animal withdraws 
itself into the shell. This peculiar appendage was described first by D’Aubenton, and 
subsequently by Miiller; and the group of shells characterised by its presence was 
formed by Draparnaud into the present genus.* 
The animal of Clausila, so far as its organisation is known, resembles that of Pupa, 
but Lamarck considered that the differences in the form and condition of the aperture 
to which I have already referred, were in themselves sufficient for generic distinction 
without reference to the presence of the clausium. On the other hand, Férussac has 
placed Clausilia in his genus Heliz, where it forms part of his sub-genus Coch/odina ; 
and M. Deshayes has been induced, by the resemblance between the external characters 
of the animals, by the similarity of their habits, and by the gradual passage from the 
one genus to the other by intermediate species, to propose the union of the two genera. 
Unless, however, peculiarity of structure or form in the shell is to be altogether 
disregarded, the presence of so singular an appendage as the C/ausium must surely be 
considered as sufficient ground for the separation of this genus. 
Nearly two hundred living species, mostly small shells, are known; several are 
found in this country, but they occur in great profusion in Southern Europe ; the larger 
species belong to tropical climates. 
Only three fossil species I believe have as yet been described; viz., C. antiqua, from 
the Freshwater limestone of Ulm; C. maxima, from the neighbourhood of Dax, and 
C. campanica, from the Freshwater limestone of Provins, in which the Paleotherian 
remains occur. 
No. 28. CLAuSsILIa STRIATULA. F. £. Edwards. Tab. XI, fig. 6 a—A. 
Cl. testa subturritd, cylindracea, ad utramque extremitatem attenuatd, transversim 
lineata : anfractibus numerosis, plano-convewis, ultimo ad basin porrecto ; apertura ovato- 
pyriformi, obliqua ; peristomate soluto, parum reflexo : lamellis quinque, duobus margine 
externo, tribus margine columellari, instructo. 
A: cylindrical, subturreted shell, attenuated at each extremity ; the whorls are very 
slightly convex, and covered with numerous rather oblique raised lines, separated by 
broad rounded sulci, occasionally confluent ; the last whorl detaches itself, and projects 
obliquely forward, terminating in an ovate, pyriform aperture, the margins of which 
are free, and a little reflected. The outer lip presents two unequal plait-like teeth, 
the smaller one near the middle, the larger one near the posterior angle of the 
* A particular account of the Clausium has been given by Mr. Miller, in the ‘Annals of Philosophy,’ 
vol. i, p. 378; and by Mr. J. E. Gray, in the ‘Zoological Journal,’ vol. i, p. 212. 
