FAMILY 2. COLIMACEA. 1 
CLAUSILIA, Draparnaud. 
Testa elongato-turrita, fusiformis, sinistrorsa, apice obtusiusculo, an- 
fractibus plurimis, gradatim majoribus ; apertura irregulari, rotun- 
dato-ovata, plicis dentiformibus, ossiculoque testaceo sive clausio 
instructa ; marginibus undique connatis, labro reflexo. 
The Clausiliz are so called on account of their shells being furnished 
with an elastic bony appendage, attached to the columella by a slen- 
der pedicle for the purpose of closing the aperture. One or two species 
exhibiting this peculiarity were noticed as early as the middle of the last 
century by Daubenton ; but Draparnaud was the first to create a new 
genus for their reception. Since his time several species have been re- 
ferred to Clausilia, by Lamarck and others, that are entirely destitute of 
the clausium ; Lamarck, indeed, adopts the genus upon the character of 
the margin of the aperture being continuous and reflected back, without 
reference to the presence or absence of the character by which it was 
originally distinguished. These have been separated by Guilding under 
the title of Siphonostoma, and by Pfeiffer under that of Cylindrella ; but, 
for our own part, we think it as well to refer them to the genus Pupa, 
reserving the name, as originally intended by Draparnaud, for those spe- 
cies only that are provided with the clausium. This organ is supposed 
by some naturalists to be analogous to the operculum of several mollus- 
cous genera, but it is an opinion which has been contested, and we think 
successfully, by Gray, upon the following argument: ‘‘ First, it is not 
attached to the animal, as the operculum always is, but is a mere appen- 
dage to the mouth of the shell. Secondly, it is only formed when the 
animal has reached its full growth, when it is about to complete the 
mouth of its shell, and not developed in the embryo of the animal while 
yet in the egg, as is the case with the operculum. Thirdly, the genus 
belongs to a group of animals which are never operculated.” 
