100 M«. W. K. PARKER ON THE STRUCTURE AND 



tliey each grow into a large falcate tract which nearly reaches the end of the 

 fontanelle, and then come within a moderate distance of each other, near the middle. 

 The roof of cartilage has a concave edge behind, as well as in front ; and from the 

 curved tracts of bone the cartilage runs forwards on each side to the end of the 

 fontanelle, and exists, between the prootic and girdle-bone, as an obliquely four-sided 

 sjjace, which occupies about a fourth of the orbital edge of the skull. 



Below (fig. 6), the prootics and ex-occipitals being of less extent, the cartilage is 



present as a large wedge on each side running into the floor of the skuU ; nearly the 



whole vestibular floor is unossified, and in front of the ear, the prootics, not completely 



surrounding the foramen ovale (V.), leave a tract of cartilage which surrounds the whole 



•of the optic fenestra (II.). 



The outer edge of the girdle-bone {<-t]i.) margins lialf the orbital rim; it is only 

 typically developed as to extent, a clear tract of cartilage separating it from the 

 orbital fenestra; while in front it only just reaches the long septum nasi (s.n.). 



This bone is large, because of the width and size of the matrix in which it is 

 formed, and not because of overpassing its own pi'oper territory, as in several kinds 

 of Anura. 



On each side the ethmoid bone does not quite cover the wings of the ethmoidal 

 cartilage (fig. 5, pa.), from which the ethmo-palatine bars are extended; these transverse 

 bars and all the huge nasal region, are left unossified. 



The roof of the nose (fig. 5, al.sp.) is very wide and enlarges from before, backwards ; 

 the floor of the nose (fig. 6, s.n.l.) is equally wide, and lessens from before, backwards. 

 Here we see what has taken place since the larval stage — viz. : that the huge cornua 

 trabeculjB are now united together by a solid intertrabecular tract, ending, in front, in a 

 rounded knob ; whilst near this knob, on each side, a small ligidar fork has been 

 given oS" which passes between the laminre of the premaxillary ; this small secondary 

 " cornu" is the pro-rhinal {p.rh.). Above (fig. 5), the nasal roof throws the external 

 nostrils (e.9i.) far apart ; each lamina has a rounded emargination behind the nostril, 

 and then expands again until it passes into the substance of the ethrao-palatine 

 band (fig. 5, i^a.) 



That band is twice the normal width, and spreads externally into a large fan-shaped 

 plate (fig. G). 



The hind horn of this expansion (pt.2X(.), as it passes into the pterygoid, becomes a 

 mere thread, and the rest of the arch, although normal, is very feeble, and its two 

 forks, the pedicle and quadrate region (q.c), are short. 



In this species it is not difficult to detach tlie palatine and pteiygoid bones (pa., 

 2)g.), for they graft themselves only sliglitl}'- on the cartilage within. The palatines 

 (fig. 6, pa.) are flat, lathy bones, rounded only at their inner end; they are sub- 

 sigmoid, with sinuous edges, and an abrupt outer end ; their inner ends pass largely 

 under the face of the girdle-bone. 



The pterygoids (figs. .5 and G, pr/.) are but little larger than the palatines ; they 



