MR. T. W. BRIDGE ON THE OSTEOLOGY OF POLYODON FOLIUM. 
733 
PLATE 56. 
Fie - . 4. View of ventral surface of cranium. Life size. 
O 
Fig. 5. View of upper surface of chondrocranium when the insisting parostoses have 
been removed. Life size. 
a.m.f. Anterior median fontanelle. 
f.g. /-shaped groove. 
liy.g. Groove for head of hyomandibular. 
p.f. Parietal foramen. 
y. Superior opening of first visceral cleft. 
(f). Upper and posterior extremity of the oblique ridge. 
Fig. 6. Vertical and longitudinal section. Reduced one-half. 
B. Canal lying above spinal canal. 
ar'. and pv . Anterior and posterior root of first spinal nerve. 
p.sc., a. sc., h.sc. Foramina by which the anterior and posterior vertical 
and the horizontal semicircular canals leave the recess in which 
the membranous vestibular sac lies. 
Ca. Carotid foramen. 
Py. Pituitary fossa. 
Fa. Foramen by which the facial nerve leaves the cranium. 
h.c. Haemal canal. 
n.c. Notochord. 
PLATE 57. 
Fig. 7. Side view of the otic capsule, which has been dissected to show the semi- 
circular canals and their relations to the parietal foramen, and pterotic and 
opisthotic bones. Natural size. 
a. Oblique ridge, terminating above and behind in the decurrent flap of 
cartilage (f>. 
Fig. 8. Mandibular and hyoid arches, and opercular bones. Life size. 
mt.pg.l. Metapterygoid ligament. 
Fig. 9. Branchial arches. 
r.v' . Bays attached to first and second epibranchials. 
