24(> MR. W. K. PARKER ON THE STRUCTURE AND 



nasals by their broad front edge, and tbe four bones, where they approach, leave a 

 lozenge -shaped tract of the girdle-bone uncovered. 



The nasals (figs. 8, 10, n.) are very large, very convex, and cover neai'ly as much, 

 ground as in the Chelonia.' They are wide over the short facial process (fig. 10), meet 

 at the middle, and leave, at their round, serrate, fore margin, the external nostrils, 

 and front of the muzzle, bare. Notwithstanding the breadth of the muzzle, the 

 premaxiUaries (px.) are not large in the transverse direction, nor are the maxillaries 

 (rax.) over large and high ; the jugal process is curved downwards to meet the small 

 quadrato-jugal {(J-j-), which is slightly grafted on to the quadrate. 



The squamosal {sq.) is but a modified " preopercular," with two short "horns," 

 above, a postorbital, and a supra-temporal, spur ; most of the bone is the descending 

 bent splint to the suspensorium or quadrate ; under the nostril, and its protecting 

 labials (fig. 10, e.n., u.l^:u.l~.) there is a noticeable septo-maxillary (s.mx.). 



The parasphenoid (figs. 1), 10, jx<.s.) is very large and broad, and a good depth 

 under the optic nerves (II.) ; it has the outline, on a smaller scale, of the whole 

 cranial " boat," of which it forms the outer coating, save that it does not dilate in 

 front ; it is, however, very broad to the end, and is strongly clamped by foui' bones, 

 viz. : the two inner palatines and the two vomers. These latter bones (v.) are flat, 

 falcate, notched, in front, where they turn outwards, and touch the maxillaries ; they 

 are some distance apart ; have no thick hind lobe, for they bear no teeth. They are 

 quite as much in front of, as inside, the internal nostrils («.«.), which are transverse, 

 and reniform with the " hilus " behind. 



The more important modifications of this skull, as compared with the ti/pe, are as 

 follows : — 



1. The general form, which is very short, wide, and deep. 



2. A single, not large, fontanelle. 



3. The more extensive ossification of the endocranium, the occipito-otics being 

 contmuous, and the right and left masses auchylosed, below ; also the great extent of 

 the girdle-bone. 



4. The extent and narrowness of the " jiarotic wings." 



5. The great breadth of the muzzle and the wide space between both outer and 

 inner nares. 



6. The absence of the almost universal dividing bar across the passage for the 

 9th and 10th nerves which arise, in this " Order," from a single ganglion. 



7. The short pedicle, and long, but little retreated, quadrate region. 



8. The double palatine bones. 



9. The obliquity of the annulus tympanicus, and the very small cavity and 

 opening. 



10. The large stapes. 



11. The great length of the columella, and its orbicular extra-stapedial. 



12. The longitudinal subdivision of the lower part of the hyoid bar. 



