18G 
MrZZLE AND FACIAL GROOVES. 
Fig. 3oS. — Ventral aspect of 
Limmca sta^nalis \?ix. Jragilis 
showing the mouth and the at- 
tenuate anterior margin of the 
head, known as the Chaperon or 
Hood. 
The ]\IuzzLE or Prostoiiiium is the region anterior to the base of the 
tentacles anti projecting in front of tlie month ; it is the essential 
})art of the head, and intimately connected 
with the power of forward locomotion in a 
detinite direction and with the general 
orientation or carriage of the body, and, 
in the Gastropoda, is generally short, some- 
what convex and angnlated at each side, 
while its attenuate anterior margin was dis- 
tinguished by Draparnand as the Chaperon 
or Hood. This feature is very perceptible 
in the species of the family Linuntidw. 
The muzzle may, however, as in Cjcloxtoma , he produced into an 
elongated and somewhat annulate pre-oral structure or Itostrnm, of a 
more or less cylindrical shai)e, sometimes dilated or slightly cleft at its 
distal extremity, which jiossesses lips and 
other oral organs, and is snscei)tihle of a 
considerable amount of elongation and con- 
traction, Imt not being a retractile organ it 
cannot he withdrawn within the l)ody cavity, 
although its parts are so strongly contractile, 
that when contraction takes i)lace, the mouth is so drawn in as to lie 
at the bottom of a distinct depression. 
None of our native si)ecios jtossess the introvertihle or truly retrac- 
tile Prol)o.scis, which seems more particularly to characterize the 
carnivorous Strei)tonenres. 
In the Pelecyi>(Hla, the portion of the body anterior to the month, 
which embraces the region of the anteri(jr adductor, may be regarded 
as rei)re.senting the Prostoiniiim. 
'I’lie I’ac'I al Grooves are an extension of the symmetrically arranged 
yet intricate plexus of channels distributing the mncns over the body, 
j and show upon the face or muzzle, in 
some si)ecie8, as two little central and 
parallel longitudinal channels, which are 
prolongations of the dorsal grooves and 
N'arionsly ramify over the anterior snr- 
Auialia stnverhyi X 2. faCe of the lllllZzle. 
In Amal'ui ><oirerhiii the two dor.sal channels clearly show upon the 
forehead, and each usually throws off outwardly a delicate branch 
Fig. 350. -Ventral aspect of the 
contracted rostrum of Cyclostojna 
clcgiX7is X -1 (after Simroth). 
Fig. 3G0, — Facial Grooves of 
