44 CLASS II]. GASTEROPODA. ORDER III. CERVICOBRANCHIATA. 
aperta; fissura, interdum subarticulata, per totam longitudinem de- 
currente. Operculum multispirale. 
The Serpula anguina of Linnzus was selected by Bruguiére for the 
formation of this genus, on account of the longitudinal slit by which the 
shell is remarkably characterized. As, however, he was unacquainted 
with its animal inhabitant, the genus Siliquaria was still left amongst 
the Annelides ; neither Cuvier nor Lamarck proposed any alteration, but 
De Blainville ventured to remove it to a place amongst the Mollusca, 
upon the very laudable conjecture that the longitudinal fissure might 
probably be destined to answer the same purpose as the vertical perto- 
ration in the shell of Fissurella ; ‘‘ la position mediane de la fissure pourroit 
méme faire soupconner dans animal quelque chose danalogue a ce qui ce 
voit dans les Fissurelles.” ‘These suspicions were subsequently verified ; 
for upon M. Ardouin obtaining the opportunity of examining the animal, 
it was found to be a true cervicobranchiate mollusk, furnished with an 
operculum. ‘The fissure is, in fact, situated over the branchial cavity for 
precisely the same purpose as the row of perforations in the shell of Ha- 
liotis, and in like manner it becomes partially filled up and formed anew 
as the shell advances in growth. 
The shell of Siliquaria may be described as being tubular, somewhat 
cylindrical, and irregularly twisted; the posterior end is more or less 
attenuated, and loosely produced into a spire, which becomes unrolled 
towards the anterior end, the extremity being open; and the fissure, 
which is sometimes a little articulated, runs throughout its entire length. 
Example. 
Pl. CLI. Fig. 1 to 3. 
SIL1quARIA ANGUINA, Lamarck, Anim. sans vert., vol. v. p.337. Born. 
Mus: pl. 1S ea: 
Serpula anguina, Linnzeus. 
Agathirses — 2? De Montford. 
