THE SKELETON OF THE CODFISH. THE SKULL. 97 



pterotic and frontal is another rather large bone, the sphenotic, 

 this articulates below with the pro-otic. The pterotic and 

 sphenotic together give rise to a large concave surface by 

 which the hyomandibular articulates with the cranium. 

 Several of the cranial nerves pass out through the bones of 

 the auditory capsule. The ninth leaves by a foramen near 

 the posterior border of the opisthotic, the fifth and seventh by 

 a notch in the anterior border of the pro-otic. 



A number of bones are likewise developed in connection 

 with the orbit forming the orbital ring. Of these the most 

 anterior, the lachrymal, is much the largest, the others are 

 five to seven in number, the most ventral being the suborbital. 

 The sclerotic coat of the eye is cartilaginous. 



Two pairs of bones and one unpaired bone are developed in 

 connection with the olfactory capsules, of these, the nasals 

 are narrow bones lying next the lachrymals, but nearer the 

 middle line ; they overlap the second pair of bones, the ir- 

 regular lateral ethmoids. These meet one another in the 

 middle line, and are overlapped behind by the frontal. They 

 articulate laterally with the lachrymal and palatine, and ven- 

 trally with the parasphenoid. 



In a posterior view the foramen magnum and the four 

 bones which surround it and together form the occipital seg- 

 ment are well seen. On the ventral side is the basi-occipital, 

 terminated posteriorly by a slightly concave surface which 

 articulates with the centrum of the first vertebra. The sides 

 of the foramen magnum are formed by the exoccipitals, a 

 pair of very irregular bones, pierced by a pair of prominent 

 foramina for the exit of the tenth nerves. The exoccipitals 

 also bear a pair of surfaces for articulation with corresponding 

 ones on the neural arch of the first vertebra. The most dorsal 

 of the four bones is the supra- occipital. 



On the ventral surface of the cranium in front of the basi- 

 occipital is seen the parasphenoid, a very long narrow bone 

 which underlies the greater part of the cranium. Behind, it 

 R. 7 



