THE ELASMOBRANCHIl. 



113 



of an Elasmobrancli consisting-, exclusively, of cartilaginous 

 representatives of the primary palato-quadrate arch and of 

 Meckel's cartilage. 



The former of these, the so-called upper jaw, may either 

 be represented, as in the ChimcBra (Fig. 33), by the anterior 

 portion (^, D) of a triangular cartilaginous lamella, which 

 stretches out from the sides of the base of the skull, and is 

 continuous with the representative of the hyomandibular sus- 

 pensorium ; or there may be, on each side, a cartilaginous bar 

 inovably articulated in front with the fore-part of the skull ; 

 and, posteriori}'-, furnishing a condyle, with which the ramus 

 of the lower jaw, representing Meckel's cartilage, articulates. 



In the latter case, which is that met with in the Sharks 

 and Rays (Figs. 34 and 35), a single cartilaginous rod {g) is 

 movably articulated with the skull, in the region of the peri- 

 otic capsule, upon each side ; and, by its opposite extremity, 

 is connected by ligamentous fibres both with the palato- 

 quadrate (A) and with the mandibular or Meckelian cartilage 

 {Mn). This cartilaginous siisj)e)isoriwn represents the hyo- 



fiG. 83. — Vertical section of the skull of Chimcera monstrosa, -without the labial and nasid 

 cartilag-es: ^1, the basi-occipital region; P, the pituitary fossa ; iV^a, partition between 

 the olfactory sacs ; B, alveolus for the anterior upper-jaw tooth ; C, D, the region of th« 

 triangular cartilage which answers to the hyomandibular and quadrate ; D, B, that 

 which answers to the quadrate, pterygoid, and palatine ; J/>i, the mandible ; / Or, the 

 interorbital septum; asc and/>sc, the anterior and posterior semicircular canals; I., II., 

 v., VIII., exits of the olfhctory, optic, fifth and eighth pairs of nerves. 



mandibular and the symplectic bones of the Teleostel^ and 

 gives attachment to the hyoidean apparatus (-Sy). Tlie lat- 



