140 MR. W. K. PARKER ON THE STRUCTURE AXD 



In the architecture of their skull they are as nearly much contrasted as any two 

 species that can be found in the wliole group of the Anura ; we shall see how much of 

 this is due to the feeble condition of one, and to the stout, stony strength of the other. 



In the skuU o£ Felobates (Plate 25, figs. 5-11) the length of the skull as compared 

 to its greatest breadth is only as 7 to 8f ; the occipital condyles project so far beyond 

 those of the quadrate that the median length is one fourteenth greater than the 

 extent of the skull at the sides. 



Here we miss the excessively wide gape of Xenophrys and the American Bull- 

 frogs ; thej^e, all was for elasticity ; here, all is for compactness. 



The occipital region is moderately wide ; the great width of the skull is mainly due 

 to the suspensorial structures (w/., q.). 



The endocranium, best seen from below, and the end (figs. 6 and 8) is wide, but 

 not flat as in Xenophrys (Plate 23, figs. 5-7) ; yet it increases in width from behind, 

 forwards, as in that type ; it has also a very broad but short nasal region, which is, 

 as in Xenophrys, a well-fused convex mass, with a thick, short, decurved " prenasal 

 rostrum" overhanging the front ; but the premaxillaries under the skull are more 

 normal. Strong as are the outworks (ectocranial elements) of tlie skull, the equally 

 strong endocranial territories can be made out very clearly, on tlie whole, without 

 unroofing. 



The occipital condyles (figs. G and 8, oc.c.) are large, sub-reuiform, postero-inferior 

 in position, and separated by a space two-thirds their width, which is gently emar- 

 ginate. The whole occipito-auditory region, right and left, is completely ossified up 

 to the foramen ovale (V.) ; the super- and basioccipital tracts of cartilage are quite 

 obliterated. There is cartilage from the front of the foramen ovale to the front of the 

 optic fenestra (II.), and then the girdle-bone {eth.) occupies all but small supero- lateral 

 tracts in the front ; the sides of the nasal region, only, are unossified. The girdle-bone 

 thus occupies the fore part of the orbito-sphenoidal region, all its own territory, and 

 all the middle part of the nasal. 



Yet the terminal part was probably formed by a separate centie (or centres), 

 as in Xenophrys, anchylosis taking place afterwards. 



From whatever aspect the endocranium is examined (figs. 5-8) great strength is 

 seen, the end view (fig. 8) especially shows how strong the occipital arch is, terminated 

 by the large condyles, and flanked by the massive auditory capsules. These show the 

 large arches of the canals {a.s.c, h.s.c, p.s.c.) ; on the outside right anfl left, the two 

 "tegmina" (fig. 5) are clamped by the large squamosals (sq.) as in a vice. 



The outspread girdle-bone (etli.) has shallow "axils," and sharp angular wings; 

 these articulate with the palatines {po.). The ali-nasal cartilages (figs. 5, 7, alji, 

 n.n>.) ai'e crescents of cartilage outside the double bony roof, nasal and prenasal; and 

 the external nostrils (e.«.) are half embraced by their concave edge; these openings 

 are well finished in front and at the side by the normal inner and outer upper labials 

 ('^/'. "./■-.). Below (fig. (i), we see that tlic bifurcate coriuia trabeculse — pro-rhinals 



