5*4 



PISCES FISHES. 



roof. Compared with the skull of a cod or of a higher 

 Vertebrate, that of a skate is simple ; it is not ossified, nor 

 divided into distinct regions, nor has it anything corre- 

 sponding to the investing membrane bones, which in higher 

 animals are added to the original foundations of the skull, 

 nor do the visceral arches in the skate take part in forming 

 the skull, which arises, as usual (see p. 459), from para- 

 chordals, trabeculae, sense capsules, etc. 



The visceral arches are primitively supports for the 

 wall of the anterior part of the food canal, but the first 



t>. br. 1. 



I I / 



Khr.l. 



Ur.1. 



w \ 



ll. 



FIG. 246. Side view skate's skull. 

 -After W. K. Parker. 



/i., First labial cartilage; n.c., nasal capsule; a.o., antorbital ; 

 p.pt.q., palato-pterygo-quadrate ; M.c., Meckel's cartilage; 

 h.m., hyo-mandibular ; e./i., epi-byal ; c.h., cerato-hyal ; /i./i., 

 hypohyal ; h.br.i-$, hypobranchials ; c.br., ceratobranchial ; 

 e.br., epihranchial ; p.br.-i, first prebranchial ; z./z., inter-hyal ; 

 ui.pt., meta-pterygoid ; 2, 5, 7, foramina of exit of the corre- 

 sponding nerves. 



two of them are much modified in connection with the 

 jaws. 



The upper jaw of the skate is a strong transverse bar, 

 formed from the union of two palato-pterygo-quadrate 

 cartilages. The lower jaw is a similar bar formed from 

 the union of two Meckel's cartilages. 



From the ear capsule to the articulation of upper and 

 lower jaw there extends on each side a club-shaped cartilage, 

 which connects the jaws with the skull, known as the 



