$ 213. 
THE CEPHALOPHORA. 241 
CHAPTER V. 
DIGESTIVE APPARATUS. 
§ 213. 
The highly-developed digestive organs of the Cephalophora always com- 
mence at the anterior extremity of the body, with a round, oral orifice, 
which is surrounded with tumid lips, but rarely has special prehensile 
organs.” These lips are quite contractile, and can evert and invert the 
mouth; with many species, they can be prolonged into & cylindrical pro- 
boscis. The walls of the oral cavity are very muscular, aud, with the 
majority of the species, form a round and often very large pharynx. The 
epithelium of this cavity is frequently developed into collars or callosities 
which serve as masticatory organs. With some Gasteropoda, this apparatus 
is composed of two horny, lamelliform jaws, which have a truncate, convex, 
internal border, and move upon each other in a lateral manner. These 
jaws are situated, sometimes directly behind the oral orifice, and sometimes. 
at the base of the pharynx. 
Many other Gasteropoda have only an upper jaw enchased in the roof 
of the oral cavity, and which is easily seen from its deep-brown color. It 
consists of a transverse, sewilunar, horny plate, upon whose anterior surface 
are several vertical crests, which terminate upon the free border by as. 
many tooth-like processes. 
Nearly all thé Cephalophora have a longer or shorter fleshy mass, ad- 
hering to the base of the pharynx, and which is sometimes grooved longi- 
tudinally ; it is quite comparable to a Tongue. Sometimes it is very large 
and contained in a membranous sheath at the base of the pharynx. It is 
always armed witb horny, denticulated spines and plates, which are very deli- 
cate, and arranged in quite elegant, longitudinal and transverse rows. The- 
1 Such are the tentacular appendages which have 
a sucker, of Pterapoda (Clio, Spongiobranchaea, 
and Pneumodermon), already mentioned above 
(§ 204. 
o There is a retractile proboscis with Pneu- 
modermon, Spongiobranchaea, Pterotrachea, 
Thetis, Buccinum, Dolium, Cypraea, Murer, 
Conus, Voluta, and many other Pectinibran- 
chia. 
8 The external borders of these jaws are easily 
perceived between the lips, as with Scyl/aea (Cu- 
vier, Mém. loc. cit. fig. 6, a. 6, b.), with T'ritonia 
(Savigny, Descript. de Egypte, Hist. Nat. IT. 
PL. IL. fig. 111°, and Dedle Chiaje, Descriz. loc. 
cit. Nav. XLII. fig. 1), and with Diphyllidia and 
Bulla. They are found also directly behind the 
lips with Venilia, Aeolis, Amphorina, and Ter- 
gipes (Alder, Hancock and Embleton, Ann. of 
Nat. Hist. XIII. p. 162, Pl. II. fig. 3, 4, XV. p. 4, 
Pl. IL. ; also Quatrefages, Ann. d. Sc. Nat. I. p. 
* [ § 213, note 4.] For many details upon the 
oral organs of the Helicina, of an anatomical as 
well as a zoological import, see T'roschel (Ueber 
147, Pl. V. fig. 5, and Nordmann, loc. cit. p. 12, 
Tab. I. fig. 7). With Dentalium, on the contrary, 
the jaws are situated at the base of the oral cavity 
(Deshayes, \oc. cit. p. 333, Pl. XV. fig. 11, b. b. 
15, 16, or in the Isis, 1832, p. 463, Taf. VI. fig. 15,. 
19, 20). 
4 This upper jaw is particularly developed with 
the Limacina and Helicina ; see Cuvier, Mém. joc. 
cit. Sur la Limace, &c., Pl. IL. fig. 4 (Limaz) ; 
Troschel, in Wiegmann’s Arch. 1836, I. p. 257, 
Taf. IX. fig. 3-9 (Arion, Limazx, Helix, Clau 
silia, and Succinea), and Erdl, in Mor. Wag- 
ner’s Reisen inder Regentsch. Algier. III. p. 268, 
Yab. XIII. XIV. With Lymnaeus, and Planor- 
bis, there are, beside, two small lateral jaws ; these 
exist also with Valvata, and Paludina, where the 
upper jaw is wanting. With Zephyrina, there are 
also three jaws at the base of the pharynx; see 
Quatrefages, loc. cit. I. p. 132, Pl. V. fig. 1.* 
die Mundtheile einiger Helicien, in Wiegmann’s 
Arch. 1849, p. 225).— Ep. 
