THE SKELETON. 



535 



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 MeckePs 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 hyo- 

 mandibular or suspensorium. It is the upper half of the 

 second arch. Attached to it is a slender four-jointed rod 

 the lower half of the hyoid arch. 



FIG. 281. Side view of skate's skull. 

 After W. K. Parker. 



/!., First labial cartilage; H.C., nasal capsule; a.o. t antorbital; 

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

 A.m., hyo-mandibular ; e.h*, epi-hyal; c.k., cerato-hyal; h.h. t 

 hypo-hyal ; h.br.i-^ hypobranchials ; c.br., ceratobranchial ; 

 e.&r., epibranchial ; fi.br.i., first prebranchial ; i.k., inter-hyal ; 

 nt.pt., meta-pterygoid ; a, 5, 7, foramina of exit of the corre- 

 sponding nerves. 



Then follow five branchial arches, each primarily four- 

 jointed, forming the framework of the gill-bearing region. 



Of less importance are the labial cartilages about each 

 nasal capsule, an antorbital cartilage uniting the nasal 

 capsule with the end of the pectoral fin, and a spiracular 

 or meta-pterygoid cartilage supporting the rudimentary gill 

 in the spiracle. 



The pectoral girdle forms an almost complete hoop of 



