Vertebroid Homologies of the Qrafnmm in Vertebral i a. 55 
which is subsequently so incorporated with both the basi- 
occipital and sphenoid, that Soemmering described them as 
a single bone spheno-occipital or basilar in the adult con- 
dition of the cranium. The petrous is early developed, 
and besides forming the hyp-otic 6 and 9 the pro-otic, 
contains the otic capsule. The ossification begins in these 
in a chondrous state, about the same time as the ossi- 
fication of the kaulon. The parietals are ossified in mem- 
brane. 
(iii.) The Axo-presplieno Bivertehra, or the Anterior Spheno- 
orhital (Beclard) ossifies very early in foetal life, at the margin 
of the foramen opticum, and extends along the ingrasial 
wings 18. These are afterwards united in the centre. 
Towards the close of foetal life this vertebra is closely united 
with the sphenoid, and is usually in Anthropotomy described 
as part of that bone. 
The Atlo-sphenoid centrum 12 with the rostrum 12', and 
the pedicles of the wings, are ossified in cartilage, but the 
ala major results from membrane. The ossification begins in 
the sphenoid soon after the occipital, and is developed from 
many centres. Beclard divided these into two classes : — 
1. The posterior or spheno-temporal includes the ala major 
16, where the first nuclei are seen anterior to the foramen 
rotundum, from whence the ossification extends outwards 
and upwards into the alse majores, and downwards into the 
pterygoids 36, 37. About the same time there are two 
ossific points for the centrum 12, and the lateral projection, 
as described by Meckel, and copied in " Quain's Anatomy" 
(fig. 26, b. 5). 
(iv.) The Ethmo-frontal Bivertehra— ThQ perpendicular 
plate of the ethmoid extends through the atlo- frontal, arising 
from the frontal protuberance, and forming the axoid portion. 
The ossification of the frontals or the atloid portion com- 
mences early in membrane, by a central point in each half. 
They are separate till birth, and in females often remain so 
during life. 
(v.) The Apo-cranial Bivertehra is formed by the nasal pro- 
montory 22, with the nasal spine continued into the septum 
nasi 24 axoid. 
