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 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 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. 
Fic, 281. —Side view of skate’s skull. 
—After W. K. Parker. 
éx., First labial cartilage; 2.c., nasal capsule; @.o., antorbital; 
p.pt.g., palato-pterygo-quadrate; .c., Meckel’s cartilage; 
h.m., hyo-mandibular; ¢.4., epi-hyal; ¢.4., cerato-hyal; 4./., 
hypo-hyal ; %.67.1-5, ypobranchials ; ¢.d., ceratobranchial ; 
e.6r., epibranchial ; 4.47.1., first prebranchial ; 2.4., inter-hyal ; 
m.pt., meta-pterygoid ; 2, 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 
