15 



mentiuned. Two oi' three pairs of foramina for the transmission of the 

 statocystic nerves pierce the ventral wall of the eapsnle. A foramen at the edge 

 of the depression foi- the pedal ganglion transmits the nerve of the crista. 

 Another foramen , for the macular nerve . is situated a short distance inward 

 from the foramen for the eristic nerve. 



Just in front of the statocysts, two pairs of foramina iiierce the cartilage 

 at the base of the pedal process: one pair allows the siphonal nerves to pass 

 from the pedal ganglion to the siphon; and the other, which is in front of the 

 preceding and is just exterior to the lateral ligaments, transmits a paii- of veins 

 from the orbital sinuses to the anterior vena cava. Several small foramina 

 which are represented in the drawings but which do not merit description , 

 transmit small blood-vessels and nerves. 



The two preorbital cartilages (Plate I Fig. 1) are attached side by side to 

 tlie pedal process of the skull and reach outward and forward between the eyes 

 and the pharynx. Each cartilage is a 

 flattened , stocking-shaped bar whose "^ 

 tip (toe) projects downward. This bar 

 lies against the inner surface of the 

 ej^'e and supports certain muscles of 

 the eye. 



The nuchal cartilage (text figure 5) 

 lies in the muscles of the liver case '^' ' ' 



between the liver and the ventral end of the pen with which it articulates. It 

 is a thick , quadrangular , trough-shaped plate. Two of its angles are directed , 

 one forward , and one backward , and the lateral angles are bent downward 

 around the liver. On the upper side of the cartilage there is a linear grooved 

 surface w^hich articulates with the pen. This articular surface has three grooves, 

 of which the two lateral , articulate with the edges of the pen. The upper 

 edges of the lateral siphonal valves are attached to the cartilage just below the 

 articular surface; the cephalic retractor is attached to the ventral edge of the 

 cartilage: and the nuchal retractor is inserted on the dorsal edge and on the 

 greater portion of the lo\ve]- surface of the cartilage. 



The postcephalic oi- "diaphragmal" cartilage is a thin oval plate which lies 

 just behind the head in the lower wall of the liver-case between the liver and 

 the anterior vena cava and stiflfens the liver-case. 



Each tin cartilage lies at the base or inner side of the hn. These will be 

 further described in connection with the fins (text figure 7|. 



The siphonal cartilages are a pair of grooved linear plates attached to the 





