DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 14S 



(icl.^) hardly as large as usual. Attached to this cartilage is the second or outer labial 

 {u.l.^); it, also, is crescentic and solid ; its concave face lies towards the nostril. 



Below this, and wedged in between the premaxillary and maxillary, there is a 

 granular septo-maxillary (fig. 7, s.mx.). The fore margin of the high, long, and thick 

 maxillary (mx.) is notched where it receives the small bone ; its greatest height is 

 where the nasal wing rests obliquely upon, and is sutured to, it. Tlie upper surface 

 is cut away in crescentic manner, and this margin and the orbital edge of the frontal 

 region, together, form most of the oval orbital space ; it is only deficient where the post- 

 orbital process fails to meet the antero-superior angle of the squamosal (sq.) in the 

 temporal region ; the temporal muscle is thus uncovered at its " origin." 



Behind the suborbital margin the maxdlary rises to form a suture with the post- 

 orbital process of the squamosal, and then lessens to its end, which is a blunt point 

 overlapping the quadrato-jugal (q.j.) This latter bone is high, thick, and quite one 

 with the ossified quadrate region ((/.). 



The squamosal (figs. 5, 7, 8, sq.) answers well to the rest of the outer garniture of 

 this strongly-built skull ; its facial granular plate is large, oblique, has two large 

 rounded emarginations above, and a lesser round notch below. Its stem (tig. 7) is 

 strong, sinuous, and notched below ; its supra- temporal tract runs over the tegmen 

 tympani, binding hard upon the prootie, up to the horizontal canal [h.s.c), to the form 

 of which it Ls adapted. The end view (fig. 8, sq.) shows how solid and convex this 

 bone is, and what a stout knee its " pre-opercular,'' or descending process makes, where 

 it binds upon and clamps the suspensorium, and articiUates witli the pterygoid by its 

 hinder edge. 



I shall compare this skull now with that of the type, as I have done with that of 

 Bambinator which has just been described. The most striking modifications here seen 

 are as follows : — 



1. The form of the skull, which is very short, high, convex, and of a regularly semi- 

 oval contour. 



2. The intense ossification of all the parts, outer and inner, and the sub-ganoid 

 condition of the exposed parts of the investing bones. 



3. The anchylosis of all the six roof-bones. 



4. The complete union of all the four occipito-auditory centres. 



5. The great extent of the girdle-bone, from the optic fenestra to the fore edge of 

 the skull. 



6. The inferior position of the premaxillaries. 



7. The obliteration of the joint of the pedicle. 



8. The lateral junction of the squamosal and maxillary. 



9. The complete ossification by the quadrato-jugal of the quadrate. 



10. The minute size and imperforate condition outwards of the Eustachian passage 

 as the tympanic cavity. 



11. No annulus tympanicus. 



