GENERAL ANATOMY OF THE SQUID. 357 



(i.) On the pharyngeal or dorsal surface of this muscle 

 notice the teeth of the lingual ribbon. This consists, 1st, 

 of a delicate suh-radular membrane, which covers the sur- 

 face of the muscle, and 2d, of the radula, or series of 

 chitinous teeth, which project into the cavity of the pha- 

 rynx. In a cross section these teeth are seen to be of 

 two kinds, 1st, a central, symmetrical tooth, the rachidian 

 tooth, which, with the rachidian teeth above and below it, 

 forms the rachis of the lingual ribbon, and 2d, on each 

 side of this a series of three lateral teeth. 



c. In a section a little farther back notice that the cavity 

 of the pharynx is completely separated from that of the 

 lingual ribbon, and the outer angles of the pharynx are 

 folded to form the superior salivary glands. 



d. In a section through the eyes, notice : 



1. The small oesophagus (Fig. 188, c), with its epithelial 

 lining raised to form longitudinal folds, which are seen, in 

 cross section, as little papillae projecting into its cavity. 



2. Ventral to the oesophagus, and enclosed in a common 

 sheath with it, the ducts of the two inferior salivary 

 glands. 



3. On the middle line of the body, between the oesopha- 

 gus and the ventral surface of the head, the cross section of 

 the heart-shaped pedal ganglia (Fig. 188, d), which con- 

 sist of a central axis of white nerve fibres, and a peri- 

 pheral layer of gray matter, or ganglion cells. 



4. Around the periphery of the ganglion notice the nerve 

 commissures (e,f), which pass from the arms into the 

 ganglia. Notice that they pass through the gray layer of 

 ganglion cells into the central white matter. 



5. On the sides of the head notice the transverse sections 

 of the eyes. 



6. The eye consists of an anterior chamber (m), and a 



