400 
ME. W. K. PARKER ON THE STRUCTURE AND DEVELOPMENT 
Tlie articular region of the mandible is ossifying ; the rod in the middle is flattened 
somewhat, and then runs in an arcuate manner to the free end. 
The bones formed in non -cartilaginous tracts have now to be described. 
© 
In the fore half of the basis-cranii there is a sharp style of bone ; it is wedged 
between the trabeculae, and broadens out under the pituitary space ; this is the para- 
sphenoid (Plate 29, fig. 5, and Plate 30, fig. 1 , pa.s.) : it is seen in longitudinal section 
in the latter figure. 
The infero- lateral regions of the cranium have acquired two bony tracts, the frontals 
and parietals (/., p.) ; the frontals are rapidly growing round the fore part of the 
hemispheres (Plate 30, fig. 3 ,/.), whilst the parietals (fig. 5, p.) have a lower position. 
The nasals (Plate 29, figs. 3, 4, and Plate 30, fig. 2, n.) lie on the inner side of 
the nasal roofs, and dip deep down between them. 
The pre-maxillary '(px.) is seen in front of these capsules, and below the recurrent 
trabecular cornua. 
Over the large nasal gland a thin bone, the septo-maxillary (Plate 30, figs. 1, 2, s.mx.), 
is stretched ; it ascends both up the side of the septum nasi and also towards the 
nasal wall. 
Below the gland we see the vomer (v) ; it is hollow to receive it ; and between the 
two bones on the under surface there is a section of the principal upper labial (u.l). 
In the transverse section (fig. 2, mx.) the fore part of the maxillary is cut through ; 
it is a thin lath, and is seen also in the next two sections (figs. 3 and 4) ; it is shown 
from the side in Plate 29, fig. 3, mx. 
Three bones have appeared in the inner palatine fold — namely, the palatine, trans- 
palatine, and pterygoid : these are endoskeletal bones. There are also bony tracts 
outside the nasal roofs : these are the prefronto-laclirymals (pf. ) ; another pair is 
seen in older specimens, namely, the post-orbitals. 
The palatines (Plate 29, fig. 3, and Plate 30, figs. 3-5, pa.) are also thin laths of 
fibrous bone ; they are rounded in front, pointed behind, and have in front of their 
middle a thin flat coiled process, the orbital or etlimopalatine process, which arches 
over the nasal canal (Plate 30, fig. 3). 
The transpalatine (Plate 29, fig. 3, t.pa.) is a binding bar between the marginal and 
sub-marginal series ; it is a cuneiform bar passing obliquely so as to attach the 
zygomatic process of the maxillary to the pterygoid. 
The pterygoid (pg.) is a slender style, and it belongs, morphologically, to the 
mandible ; it binds the quadrate to the palatine. 
Another splint binds the quadrate to the auditory capsule (Plate 29, fig. 4, sq .): 
this is the squamosal ; it is sickle-shaped, with the point directed forwards. 
This bone already is serving as a loose swinging point for the descending and 
retreating mandibular suspensorium. 
The description of this stage may be fitly ended by a short notice of what transverse 
sections reveal of the form and relation of the elements of the chondrocranium, 
