MR. T. H. HUXLEY ON THE MORPHOLOGY OF THE CEPHALOUS MOLLUSCA. 59 
From the same point of origin a thiek bundle of reddish fibres passes up over the 
posterior extremity of the cartilages, and is inserted into the upper edge and sides of 
the ‘^elastic plate.” These may be called the intrinsic muscles (fig. 13 [m). 
This elastic plate {'/j) is an elastic transparent membrane, broad posteriorly, and 
narrower anteriorly, so as to be somewhat heart-shaped. By its superior surface it 
gives attachment to the dentigerous plate ” (lamina radulse of Midd.), on which 
the teeth are set ; inferiorly it is very smooth, and plays over the equally smooth 
pulley-like surface aflforded by the larger buccal cartilages (fig. 14). These are four 
in number, two large and two small accessory ones (S). The larger are elongated, 
white, cartilaginous-looking plates, excavated internally, and thick and convex be- 
hind ; their inner edges are kept together by strong transverse muscular fibres. Their 
upper edges are in contact, forming the smooth surface mentioned above; the smaller 
seem to be in a manner sesamoid cartilages ; they are connected anteriorly with the 
tongue-plate and posteriorly with muscular fibres, which are inserted into the larger 
cartilages. 
It is clear that the action of the intrinsic muscular bands (having the insertions 
described) must be to cause the “elastic plate,” and with it the “dentigerous plate,” 
to traverse over the ends of the cartilages, just like a band over its pulley, the carti- 
lages themselves being entirely passive in the matter. The extrinsic bands, again, must 
serve to protract the whole mass and thrust it more or less firmly against the object 
to be acted upon. 
I have examined Buccinum, Fissurella, Doris^, Aplysia, Biillcea, Helix, Onchidium, 
Cyprcea, Pteroceras, Sigaretus and Vermetus, and in all I have found a structure 
essentially similar to that here described; the difference consisting in the greater or 
less length of the dentigerous plate, and the more or less complete development and 
isolation of the buccal cartilages. These are the less distinct the more the tongue 
becomes a mere organ of deglutition. Aplysia and Bullcea, for instance, have the 
cartilages united and much softer than in most genera. The structure of the Cepha- 
lopod tongue closely resembles that ol Aplysia ; and it has the further peculiarity, that 
the portion of the floor of the buccal cavity in front of the tongue (true tongue 
of Middendorf), which is plicated and distinct in most Gasteropods'f', is in the 
Cephalopods raised up into a laminated caruncle (or several) larger than the tongue 
itself;};. 
This pulley-like structure of the tongue appears to me to be very characteristic of 
* See also the description of the “ tongue” in this genus by Messrs. Hancock and Embleton, loc. cit. 
p. 210. 
4 OsBEK, loc. cit., p. 505, describes a soft striated papilla arising from the floor of the mouth in front of the 
tongue in Patella, which, he says, “ is probably the organ of taste.” 
+ See Owen, Article ‘ Cephalopoda,’ Cyc. Anat. and Phys. Is the “ horny striated substance ” supporting the 
lingual teeth, “ which appears to represent the body of an os hyoides ” in Nautilus, the representative of the 
buccal cartilages 
