300 THE CEPHALOPODA 
As in the Amphineura, the Gastropoda, and the Scaphopoda, the 
floor of the buccal cavity is occupied by the anterior part of the 
radula, which issues from a pharyngeal caecum. Each transverse 
series of this radula is formed by a median tooth, with three 
symmetrically disposed teeth on either side; the only exceptions 
to this rule being—Nautilus, which has four teeth on either side 
(Fig. 267, A); Gonatus, which has only two teeth on either side ; 
the Cirrhoteuthidae, which have no radula and have therefore been 
named Leioglossa. In front of the radular prominence is the 
so-called “tongue,” a fleshy projection (Fig. 268, to) covered by a 
Fic. 267. 
Radula of Cephalopoda. A, asingle row of lingual teeth of Nautilus pompilius ; B, two rows 
of lingual teeth of Sepia officinalis; C, lingual teeth of Eledone cirrhosa. (From Lankester, 
after Keferstein, Troschel, and Loven.) 
somewhat thick papillated cuticle: it corresponds to the sub-radular 
organ of other Molluscs. 
The salivary glands, of which two pairs are present in many 
Cephalopoda, pour their secretion into the buccal cavity. In 
Nautilus there are no posterior salivary glands, but on each side of 
the buccal cavity there is the orifice of a gland situated in the 
buecal wall and corresponding to the anterior salivary glands of 
the majority of the Dibranchia. In the latter order all the Decapoda 
have posterior salivary glands, situated fairly far forward opposite 
the cephalic cartilage (Fig. 268, sg): they are compact, acinous, 
almond-shaped structures composed of convoluted and bifurcated 
tubes; their ducts unite immediately they leave the glands to 
form a single median duct, which runs alongside of the oesophagus 
and opens, like the duct of one of the pairs of glands in the 
Aplacophora, at the summit of the sub-radular organ. The anterior 
