364 



Vertehrata. 



five (occasionally six or seven) arches, the branchial arches, 

 a,re each divided into several pieces, and bear on their outer borders 

 delicate cartilaginous rays (removed in Fig. 301), which support 

 the septa between the gill-clefts ; similar rays are also present on the 



Pig. 301. A skull and visceral arches of a Shark, B the same of a Pike; the 

 arches are in part artificially separated ; premaxiUa and maxilla separated in B. First arch 

 dotted, second shaded : br^ — br^ first to fifth branchial bars (third — seventh visceral arches), 

 c basibranc-hials, d dentary, g palato-qnadrate, gb palatine, hm upper portion of the hyoid 

 arch (in B hyomandibular), h rest of the same, h mandible, o orbit, g quadrate, s symplectic, 

 V — v" pterygoids (v ecto-, v' endo-, v" metapterygoid). — Orig. 



hyoid).* In the G-anoidei, Dipnoi, and Teleostei, there 

 are also seven visceral arches. The upper portion of the man- 

 dibular arch, the palato-quadrate, naeets its fellow of the other 

 side in the cartilaginous Ganoids, whilst in all others it 

 remains distinct. This portion is intimately connected below, with 

 the lower end of the upper portion of the hyoid arch, which is 



* As regards visceral arches, the Bays, on the whole, resemble the Sharks, but 

 the hyoid shows certain peculiarities, which cannot be gone into more closely here. In 

 many Sharks there are anteriorly, close to the gill-bars of each side, a pair of feebly- 

 developed cartilaginous bars (the labial cartilages), which may perhaps be regarded as 

 rudimentary first visceral arches. 



