336 



CHORD AT A. 



ring posteriorly, consisting of a supraoccipital^ paired exoccipitals and 

 a basioccipital ; (2) the otic bones surrounding the auditory capsule 

 and lying immediately in front of the occipitals. There are five otic 

 bones — prootic, epiotic, opisthoHc, pterotic and sphenoHc. On the two 

 last is a large facet for the hyomandibular bone. (3) At the front end of 

 the cranium are a series of bones arising in connection with the nasal 

 capsules, the dorsal nasals^ median mesethmoid and lateral edethmoids. 

 (4) Between these and the occipital and auditory region the dorsal surface 

 of the cranium is completed by small parietals in front of the supra- 

 occipital and large frontals covering the orbits. In front of the otic 

 bones there is a pair of small alisphenoids in the orbit. (5) The basal 

 axis of the cranium is formed, anteriorly to the basioccipital, by the 

 long parasphenoid and vomer, the latter bearing teeth and lying below 



Fig. 238. — The Right Pectoral Fin and Girdle of the Cod 

 WITH BOTH Pelvic Fins. {Adnat,) 



Post-temporal. 



Postclavicle. 



Basipterygium. 



Dermal Fin-rays. 



Distal Pterygiophores. 

 Proximal Pterygiophores 

 (Brachial Ossicles). 



bJO 4) 



Fin-rays. (^ 



the mesethmoid. (6) Lastly, in connection with the orbit is a chain of 

 orbital bones, of which the anterior and largest is known as the lacrymal. 



To this cranium are loosely attached a number of bones belonging 

 to visceral arches. Anteriorly are '^2h^di premaxillcB bearing teeth, and 

 maxillce without teeth. These are supposed to be connected with the 

 labial cartilages of the skate. 



The first or mandibular arch ossifies into the palatines attached to 

 the ectethmoids, the pterygoids with meso- and iiietapterygoids, and the 

 quadrates which form the upper half (or palatoquadrate chain) and the 

 articular, angular and dentary forming the lower half or mandible. 

 An articulation is formed between the articular and the quadrate. 



The second or hyoid arch consists in its upper half of a hyomandi- 

 bular attached to the otic region, bearing four opercular bones on its 



