ESPECIALLY MYCTOPHOIDS 23 
The prootics are large, complex bones containing the trigemino-facialis chamber. 
Ventrally the prootic consists of a single sheet of bone contacting the ascending 
process of the parasphenoid. More dorsally it divides into two sheets, the inner one 
curving medially to meet its partner of the opposite side in the mid-line to form the 
prootic bridge, while the lateral sheet passes dorso-laterally to contact the sphenotic 
and the pterotic. The lateral sheet is produced medially above the prootic bridge to 
form the rear face of the orbit. The otolith chambers are closed anteriorly by the 
f.i.c.a 
Fic. 8. Apateodus striatus Woodward. Neurocranium in lateral view. From the 
collection of the Institute of Geological Sciences, number 26241. 
junction of the prootic bridge with the lateral wall of the prootic. The basioccipital 
is joined to the hind edge of the prootic bridge and thus separates the cranial cavity 
from the myodome. At about the middle of its length, the prootic bridge is pierced 
near its lateral edge, just internal to the anterior extension of the otolith chamber, by 
a foramen which transmitted the abducens nerve into the myodome. Above the 
prootic bridge the anterior, orbital face of the prootic is irregular in shape and deeply 
pitted. This part of the prootic meets the sphenotic dorso-laterally, and the pleuro- 
sphenoid and basisphenoid medially. The lateral face of the prootic contacts the 
sphenotic and the pterotic within the hyomandibular facet. 
The trigemino-facialis chamber is divided by a bony septum into a medial pars 
ganglionaris and a lateral pars jugularis. The pars jugularis is a long horizontal 
canal lying within the prootic, lateral to the pars ganglionaris. The canal opens 
posteriorly near to the rear edge of the prootic through a small elongated foramen. 
The canal widens anteriorly and opens into the rear face of the orbit. There are two 
foramina leading from the pars ganglionaris into the pars jugularis. The more 
posterior foramen is the facial foramen which transmitted the hyomandibular 
branch of the facial nerve. The more anterior foramen is the trigeminal and trans- 
mitted the trigeminal, buccal, otic, superficial ophthalmic and profundus nerves. 
The palatine nerve did not enter the pars jugularis but instead passed ventrally 
