DEVELOPMENT OF THE SKULL IN THE UEODELES. 205 



Above, the nasal process {n.px) is large, and wedged in between the nasals; it is 

 grooved, and a hole behind the groove leads to a passage, the middle nasal passage 

 {m.n.])), which reappears between the vomers below. 



The maxillaries {mx) are large and falciform ; their jugal process reaches three fifths 

 of the way towards the hinge of the quadrate (5-. c) ; the upper edge articulates with 

 the lower edge of the nasals and prefrontals (h, p-f). 



A small seed-shaped septo-maxillary (figs. 1 & 3, s.mx) is seen in the narial opening 

 {e. n) on each side. 



The dentary {d) forms full half of the mandible, and nearly reaches the angle behind 

 the splenial {spT), is very slender, but is more than half the length of the ramus. 



The inferior bones form a very elegant floor to the skull ; the vomero-palatines 

 (fig. 2, V, pa) are large trowels, which by their broad vomerine end fill all the fore palate 

 between the dilated processes of the premaxillary and maxillaries. 



The middle nasal passage [m. n.p) is seen in the middle of the vomerine suture ; the 

 internal nostrils (?'. n) are half enclosed in a semicircular notch on each vomer. 



The palatine portion of each bone {pa) is a long, sharp style, reaching from the 

 inner nostril to the widening part of the parasphenoid behind, nearly to the foramina 

 ovalia (v). 



These styles are very straight ; their outer edge clamps the outer edge of the para- 

 sphenoid {pa.s) ; and their inner edge is serrated with small recurved teeth. 



The apex of the pterygoid bone {pg) is now turned outwards, and nearly reaches the 

 jugal end of the maxillary; this point is far removed from the end of the "mecodont" 

 palatine, which, after throwing off this its pterygoid process, has grown a new process 

 parallel with the axis of the skull. 



The pterygoid bone is also trowel-shaped ; both ends are pointed ; and the wide hinder 

 part is subpentagonal : this part clamps but does not quite cover the condyle of the 

 pedicle (figs. 2 & Q,pd) ; and the " handle" carries the pterygoid cartilage (e.pg), much 

 of which it has converted into bone. The pointed hinder end of the pterygoid bone 

 binds but does not cover the round papilliform otic process (ot.p) of the suspensorium. 



The parasphenoid (fig. 2, pa.s) is a large bony scoop, whose bowl is placed behind as 

 a floor to the hind skull. 



The orbito-nasal region of the bone is twice as long as the interauditory part ; it is 

 oblong, rounded in front, and underlain by the vomero-palatines in front and at its 

 edges ; and it has an oblong elevation all along the middle. 



The hind part is subcircular, with dentate edges ; it is subconvex below, with hol- 

 lowings towards the sides ; above, on its intercranial surface, it has, coalesced with it, 

 the remains of the ossified " cephalostyle " of the notochord. 



There is a general dilatation behind ; but the basitemporal wings do not project much, 

 and are at a considerable distance from the joint of the pedicle with the basipterygoid 

 condyle (fig. 6, pd, b.pg). 



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