DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
143 
( u.l}) hardly as large as usual. Attached to this cartilage is the second or outer labial 
( u.l . 3 ); 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. The 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 maxillary 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 (q.). 
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 (fig. 7) is 
strong, sinuous, and notched below; its supra-temporal tract runs over the tegmen 
tympani, binding hard upon the prootic, up to the horizontal canal ([h.s.c .), to the form 
of which it is 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 articulates with the pterygoid by its 
hinder edge. 
I shall compare this skull now with that of the type, as I have done with that of 
Bombinator 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. 
