OF THE SKULL IN THE AMPHIBIA UEODELA. 179 



In Salamandra the lobe sent outwards from each trabecula forms the subnasal lamina, 

 and the end of the trabecula gives off in the adult the " prorhinal " process. 



The auditory capsules are still very large, relatively ; above, the anterior and posterior 

 canals (a.sc, p.sc) are surrounded by bone; and below (fig. 2) the vestibule is sur- 

 rounded on its inner side by a somewhat narrower tract. The huge semicircular canals 

 above (fig. 1), and the swelling vestibule with its enclosed otolith, give form to the 

 auditory sac ; the horizontal canal (h.sc) affects the form most, bulging over the side 

 and enlarging the fore part so as to make the sac pyriform. The stapes (fig. 2, st) lies 

 behind the middle ; it is an elegantly oval plate, and lies in a fenestra ovalis much too 

 large for it. Between the ear-sac and the occipital ring the glosso-pharyngeal and vagus 

 nerves are seen emerging (fig. 2) ; under the ampulla of the horizontal canal the 

 facial nerve (7) is seen to pass across under the otic process of the suspensorium 

 (ot.p). 



In the angle between the skull-wall and the ear-sac the great Gasserian ganglion (5) 

 can be well seen, its first branch passing beneath the ascending process of the sus- 

 pensorium (figs. 1, 3. 5, a.p) ; and in a notch on the back of the sphenethmoid the optic 

 nerve (2) runs out. The first nerves pass through the trabeculee much further forwards. 



The suspensorium still retains its early position and unossified condition. It is a 

 large multilobate mass. The transverse condyloid scooped, distal end looks forwards ; 

 from that part the cartilage thickens rapidly, and. spreads into three processes, two 

 running inwards, and one outwards and backwards. Of the inner processes, the upper, 

 or ascending process {a.p), is the smaller ; it coalesces with the side of the skull-wall, 

 near the top. 



The lower inner process is the pedicle (fig. 2, in front of 5) ; it is much larger, and its 

 round end pushes inwards, without coalescing, in front of the ear-sac ; all the branches 

 of the trigeminal nerve pass over this process. The outer or otic process (fig. 1, ot.p) is 

 raised into a curved ridge above, and this elevation winds round the front of the auditory 

 sac, halfway to the skull-wall, taking the same curve inward as the ascending process. 



The pterygopalatine bone {p.pg) is somewhat constricted behind the teeth, and ends 

 behind in a subflabelliform flap, which binds the suspensorium below ; but there is no 

 pterygoid process of cartilage growing from the suspensorium. Therefore this skull 

 corresponds, here, to the 1st stage of the Salamander's (PI. XIV.) ; and it also corresponds 

 with the lower Perennibranchs in form of the vomer in front, which is a long falcate 

 dentigerous plate, converging towards its fellow. 



The premaxillary is an elegant azygous bone, with its dentary margin arcuate, and 

 having from its top, at the middle, a thick ascending process, which ends in two long- 

 lathy nasal processes (n.px), that overlap the frontals (f) halfway to the parietals (p). 

 As in many Urodeles, the sharp notch between these two processes has in it a rounded 

 tubular cavity, the "median nasal passage," whose counterpart is to be seen in the 

 Lamprey and Hag-fish ; it is a non-functional, historical space. 



The frontals (fig. 1, /) overlie the parietals (p) as much as they are overlain by the 

 nasal processes of the premaxillaries. 



In this embryonic condition the vomers are wide apart behind, and the trabeculae are 



