15 



mentioned. Two or three pairs of foramina for tlie transmission of the 

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

 of the depression for 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 pierce 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 pair 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 

 the 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 '^ 

 til.) (toe) projects downward. This bar 

 lies against the inner surface of the 

 eye and supports cei'tain 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 which 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 cei^halic 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 lower surface of the cartilage. 



The postcephalic or -'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 stiffens the li^•er-case. 



Each fln cartilage hes at the base or inner side of the fin. 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 



