31^^ 



THE DOGFISH. PHYLUM CHORDATA 



in position to the gill bars of Branchiostoma. Each pair of half- 

 hoops forms a nearly complete hoop, which circles the body except 



Rostral cartilage. 

 \l / 



Rostral cartUage- 



Nasal capsule- 

 fan tan el le 



MesethmoLcJ 



cartilage . 

 Foramen for 

 ophthalmic nerve 



Orbit 



NotochorcL 



OccLpLtal^' condyles. 



Open/no of tube 

 from inner ear. 

 Semicircular 

 Conai ■ 



Groove for_^^^ 

 ontenor cardinal 



Sinus. V I 



Foramen magnum . \ / 



occipital condyles. 



Foramen for 

 mternal carotid 

 arteries . 



Groove for 

 carotid arterg. 



Foramen for 

 orbital(externaL 

 carat id)arCery. 



•Facet for 

 r)Qoman dibular 

 cartilage. 



Palatine bar. 



Meckel's cartilqge 

 — Basihgal ■ 

 Ceratohyal 



Htgom andibular. 



'^ ^ Hgpobronchial 

 Cartilage . 



eratobranchicUs. 



Basibranch laC, ' Fharyng obranchi al . 



Supradorsal . .____^ £ 



Neural arch. 



Vertebral foramen 



Mo to chord. 

 Transverse process 



Haemal canal 



¥\G. 240. — Dogfish. A, skull, dorsal; B, skull, ventral; C, visceral arches, 

 excluding labial and extra-branchial cartilages ; D, trunk vertebra ; E, tail 

 vertebra. 



on the dorsal side, where there is a gap. The first hoop, called the 

 mandibular arch, forms the skeleton of the jaws ; there is no 

 gill sht in front of it, but it is generally believed that a slit in 

 this position has been lost by becoming confluent with the mouth. 



