506 WALTER EDWARD COLLINGE. 
v. THE CRANIAL AND OTHER BONES. 
A brief description of the cranial and other bones of the head 
will facilitate reference to the course and distribution of the 
sensory canal system. 
The nomenclature is mainly that used by Bridge (16). 
Post-temporals (Pl. 39, fig. 1, pt.) are two somewhat 
Y-shaped lateral splints, the innermost area being much the 
shorter. Upon the surface of these elements are a series of 
canal bones, which conduct the posterior portion of the main 
canal. 
Dermo-sphenotics (Pl. 39, fig. 1, d. sph.).—The dermo- 
sphenotics are almost hidden by the development upon their 
surface of a series of much expanded canal bones. Posteriorly 
the dermo-sphenotics are bounded by the post-temporals, ante- 
riorly by the dermo-ect-ethmoids. On their inner side they 
are produced into a lateral process, the sutural margin of 
which is closely interwoven with the parietal and frontal 
sutures, 
Over the dermo-sphenotics the main canal divides into the 
supra- and sub-orbital and hyomandibular branches. 
The dermo-ect-ethmoids (Pl. 39, fig. 1, d. ec. eth.) are 
two lateral parostoses lying over the olfactory region and form- 
ing the lateral boundaries of the frontals. 
The parietals (Pl. 39, fig. 1, pa.) are two elongated splints 
on either side of the median line. They do not oppose each 
other mesially, excepting in the most posterior portion, at least 
not in the specimens I have seen. Bridge (16), however, says 
they do, and figures them so, from which it would appear that 
there is a considerable amount of variation. Anteriorly they 
dovetail with the frontals, posteriorly terminating in a number 
of fibrous-like rays. The parietals extend from the occipital 
region to just behind the orbit. They are the largest and the 
thickest of the cranial splints. 
The frontals (Pl. 39, fig. 1, fr.) lie on either side of the 
dermo-ethmoid, extending forwards for some distance. They 
