OF THE SKULL IN AMPHIBIA URODELA. 197 



The odontoid vertebra (od.v) clearly shows its three elements, and these are all grafted 

 upon the " atlantal " or second joint (•» 1). The skull is here seen to be most carefully 

 articulated to the spine. The auditory capsules are a little more protruded outwards, 

 carrying with them the suspensoria. 



The capsules are very large, owing to the great development of the three canals (fig. 5, 

 a.sc, h.sc, p.sc). The hinder ampulla gives a very swollen appearance to the capsules 

 even below (fig. 6). From this convexity we pass forwards to another, the vestibular ; 

 its ossification is advancing rapidly, leaving but little cartilage along the fenestra 

 (figs. 6 & 8). But the stapes and the window it fills are tilted now, so that they are only 

 seen obliquely in a basal view ; thus the handle, or stapedial rod (fig. 6, sp.c, fig. 8, co), is 

 getting nearer the top of the "tegmen." The relation of that rod to the facial nerve is 

 best made out by paring these parts away, and seeing them from within (fig. 8. 7, 

 pro, st). The nerve is imbedded in the prootic for some distance ; in fig. 8 its course 

 outside the bone is indicated by dotted lines up to the free edge. 



The occipito-otic bone is spread into the base of the skull, ossifying the remains of the 

 parachordals behind and the stunted ends of the trabecular in front ; a notch shows the 

 division of these two regions. In front of the foremost basal lobe the bone ensheaths 

 the alisphenoidal wall for a short extent ; thence to the optic nerve (2) the wall is soft ; 

 but in front, nearly up to the small distinct semioval ethmo-palatine (e.pa), the sphe- 

 nethmoid (figs. 5-7, sp.e) has spread. 



Directly in front of those bony tracts the trabecule, in their ethmoidal region, have 

 united ; there is a broad internasal lamina (i.n.c), gently emarginate behind and more so 

 in front. 



The suspensorium is altered in some respects ; the pedicle (pd) is a more distinct 

 swelling ; the quadrate ossification (<?) is larger ; and the pterygoid cartilage {e.pg)* is not 

 only larger, but has also changed its direction ; it now runs parallel with the inner edge 

 of the pterygopalatine bone. That bone (figs. 5, 6, p.pff) has become inordinately large, 

 and the toothed region is now confined to the outer margin of the broad trilobate 

 anterior part. This bone lessens its breadth two thirds in the hinder half; it turns 

 outwards in a pedate manner, and is now applied to the lower face of the suspensorium, 

 almost reaching to the quadrate hinge. 



The vomers also (v) are altered ; from their primary subcrescentic form (fig. 2) they 

 have now become, like those of the low Perennibranchs, straight, with an inner hook, the 

 hook and the outer margin only being dentigerous. Nearly the width of the ethmo- 

 palatine cartilages intervenes between the vomers and the pterygo-palatines. 



The parasphenoid (fig. 6, pa.s), by its splintery fore edge, nearly reaches the middle 

 nasal hole (m.n.p) ; it only very gently increases in breadth up to the basitemporal 

 region ; it then is twice somewhat produced outwards, most at the first pair of pro- 

 jections, and ends behind, a little in front of the foramen magnum, by a slightly emar- 

 ginate edge. 



* In fig. 6, PI. XX., this is lettered e. pa by mistake. 

 SECOND SERIES. — ZOOLOGY, VOL. II. 27 



