OF THE SKULL IN THE AMPHIBIA ITKODELA. 181 



it, whose convexity is backwards. The ampulla of the horizontal canal (h.sc) is hidden 

 by this ridge, for its outer end joins the squamosal (sq). That canal lies a in strong roof 

 (" tegmen ") laterally ; this is enlarged by the squamosal ; and the soft end of the " otic 

 process " (figs. 6, 7, ot.p) lies lodged between the two bones. The elegant bulging of the 

 vestibule in the same figures forms a lozenge-shaped convex tract below, bounded on the 

 inside by a sulcus, and on the outside by the " tegmen." A smaller lozenge exists in 

 the hind part of the larger ; this is the cartilaginous stapes (st), fastened to the rim of 

 the 4-sided fenestra ovalis. At the antero-internal angle of the vestibular swelling, just 

 outside the basitemporal projection of the parasphenoid, the 7th nerve escapes. 



The whole side wall, or sphenethmoid (figs. 6, 7, sp.e), is ossified from the prootic 

 (pro), with which it is ankylosed, to the nasal sac. At its hinder fourth the optic nerve 

 (2) escapes ; then there is a lesser foramen for some of the orbital nerves, and close in the 

 axil, between the wall in front and the ear-sac behind, the 5th nerve escapes. Part of 

 the unossified nasal roof (na) can be seen forming a curtain to the external nostrils 

 (e.n), and another part behind and below, attached to this, and most probably confluent 

 with it, is the ethmopalatine (fig. 6, e.pa). 



The suspensorium is much less retracted than in the Salamander (Pis. XVI. and 

 XVII.) ; the pear-shaped condyle is in front of the foramen ovale. It is nearly all 

 ossified by the quadrate (q) ; the upper part is completely hidden by the pterygoid (pg) ; 

 but the otic process (ot.p) remains as a tongue of cartilage attached to the grooved 

 " tea-men." 



The pterygoid (pg) has its short part swollen towards the skull ; this is seen to cover 

 the pedicle, when the skull is examined from below (fig. 6). The outer margin strongly 

 binds the inner face of the quadrate, and tbe bone from thence becomes a blunt style, 

 attached by a short ligament to the maxillary (mx). 



The dentigerous segment of the larval pterygopalatine bone (figs. 1, 2, p.pg) is com- 

 pletely confluent with the vomer of the same side (fig. 6, pa, v). The space between 

 these palatal bars is narrow, but gradually widens backwards. 



About a fourth of the bone (less on the left than on the right side) becomes seg- 

 mented off as a postpalatine bone. I call this a postpalatine because I cannot reconcile 

 it with the mesopterygoid *. It may, however, be the same bone, for it comes off from 

 the same part of the palatine as that which gave off the pterygoid. At any rate the 

 palatine itself, here, only answers to that curved ridge of a bird's palatine that cleaves 

 , to the parasphenoidal rostrum. 



Where these palatal beams widen there they become vomerine ; that widened part, 

 with the ethmopalatine cartilage, bound the internal nostril (i.n) behind. The bone 

 narrows again to form the inner rim of the internal nostril, and then grows into a 

 hatchet-blade, whose back has a round notch. The two notches together form an oval 

 fenestra. 



The outer bones of the fore face have an equal development of hard palate, as we see 



* In a generalized Woodpecker (Picwmnus minuius, see Trans. Linn. Soc. ser. 2, vol. i. pi. 5) I found a distinct 

 postpalatine bone. In that group the mesopterygoid is not fretted off, as in most " Carinatoe." 



SECOND SERIES. — ZOOLOGY, VOL. II. 25 



