372 



Vertehrata. 



The branchial apparatus. In Selachians the wall 

 of the buccal-cavity is perforated posteriorly^ by five^ rarely six or 

 seveUj large oblique slits on either side ; they lie in close succession, 



Fig. 307. Horizontal section 

 through the head of a Shark 

 {AcaniMas): diagrammatic. The 

 Tisoeral arches are dotted, the 

 gill lamellsB shaded, hr^, br^, 

 fcrj first, third, and fifth gill 

 bars, c septimi, g upper portion 

 of the first visceral arch (palato- 

 quadrate cartilage), h hyoid 

 arch, h body wall, I body cavity, 

 m oral cavity, it olfactory pit, 

 oesophagus, s gill rakers 

 (straining apparatus), spj first, 

 C sps fifth gill cleft. — Orig. 



Fig. 308. Horizontal section 

 through the head of a Teleostean 

 (Cod), dorsal to the mouth : 

 somewhat diagrammatic. Let- 

 ters as in Fig. 307, with the 

 exception of : g upper portion 

 of the first visceral arch (here 

 ossified), oj) operculum, sp ex- 

 ternal aperture of the branchial 

 cavities. — Orig. 



