PLATE 2 
EXPLANATION OF FIGURES 
All figures of Heterodontus francisci (natural size). 
3 A side view of the cranium. 
4 Posterior view of the cranium. 
5 A median sagittal section through the cranium, seen from the inside. 
nasal capsule has been removed. 
a.c., auditory capsule 
ch.. notochord 
f.a.c., foramen of anterior 
vein 
f.e.c’., external carotid foramen (en- 
trance to socket) 
fi.c., internal carotid foramen 
f.m., foramen magnum 
f.o.p., foramen of ophthalmicus pro- 
fundus nerve (leaving the socket) 
f.o.VII, ophthalmic foramen of VIIth 
nerve (leaving the socket) 
f.r-a., foramen for ramus anastomoticus 
artery 
f.s-m., foramen for spino-muscularis 
artery 
ft, foramen through which the ol- 
factory nerve leaves the cranium 
fJI, foramen for the second cranial 
or optic nerve 
fJII, foramen for third eranial or 
oculomotor nerve 
cerebral 
The 
/1IV, foramen for fourth cranial or 
trochlear nerve 
f.VII, foramen for seventh cranial or 
facial nerve 
f. VIII, foramen for eighth cranial or 
auditory nerve 
f.IX, foramen for ninth cranial or 
glossopharyngeal nerve 
/.X, foramen for tenth or vagus nerve 
1.0., interorbital canal 
o.cd., occipital condyle 
o.cr., occipital crest 
o.f., orbital fissure 
o-n., orbito-nasal canal (entrance to 
socket) 
pl.f., palatal fossa 
po.hm., posterior hyomandibular proc- 
ess 
po.o., postorbital process 
pr.o., preorbital process 
s.hm., superior hyomandibular process 
s.o., supraorbital crest 
48] 
