38 
ACICULIDiE. 
Dr. Gruithuisen describes the operculum as 
formed of concentric rings: this is very pardon- 
able^ as it is very easy to overlook its spiral cha- 
racter. 
Fam. 6. ACICULID^. 
Muzzle annulated^ produced. Tentacles subulate, 
not swollen at the end. Eyes large, on the back 
of the neck, rather behind, and between the base 
of the tentacles (fig. 10.). Gills vascular; jaws 
none. Foot oblong ; divided across in the mid- 
dle. Male organ large, at the hinder part of 
the base of the right tentacles, exserted like a 
third tentacle. Shell spiral, sub-turreted ; aper- 
ture oblong ; peristome simple ; outer lip rather 
dilated, sinuous. Operculum horny, spiral, of 
few rapidly enlarging whorls. Terrestrial, 
unisexual. 
On account of the shape of the shell, the animals 
have been placed with Bulimi, 
When the animal was first discovered it was then 
arranged with AuriculidcE^ on account of the position 
of the eyes. But M. Ferussac (^Dict Class. H. 
N. ii. 90.), in 1822, first noticed the operculum; 
and it has been more lately described by Mr. Alder, 
the Abbe Dupuy, and others. 
The animal is very rapid and irritable, but comes 
out of the shell with great hesitation. It carries 
the shell horizontally when it walks. Preferring 
dampness, it hides itself from the sun, secreting 
