196 PROF. W. K. PARKER ON THE MORPHOLOGY 



In the adult (PL XXI. figs. 2 & 3, st) the stapes lies close to the edge of the tegrnen 

 and its squamosal tilings, and the facial nerve (7) passes close beneath the otic process 

 of the suspensorium. 



The explanation of what is seen in these small kinds comes from the Menopome. In 

 that type, and in the Siren, there is an oval hyomandibular, over which the facial 

 nerve passes ; hut in the Menopome the columella also is very large, perfect, and 

 elegant. 



In the Menopome, the gigantic Siebolclia, my figures (to appear in the Zool. Trans, for 

 1881) show this cartilage sticking by its broad foot to the top of the suspensorium and 

 squamosal above and behind, and having its narrow end inserted into a bony stapedial 

 sheath. This cartilage is formed beneath that fold of skin which is the operculum of the 

 first cleft. That cleft, in the Selachian, is only left open above ; in the Urodeles it is 

 closed ; but in the huge types just mentioned a " pharyngo-hyal " and an " epihyal " 

 appear ; the former becomes the " columella ;" in the Frog both elements are included 

 in that rod *. 



The main difference between the fore part of the skull of the youngest larva of 

 Spclerpes salmonea and that of S. rubra (figs. 1-4) is the slender face and more advanced 

 condition of the specimen. 



We have now the right and left moieties of the sphencthmoid (fig. 3) ; for close 

 behind the ethmo-palatine buds (e.pa) the skull-wall is ossified : these growths are still 

 soft. The internasal lamina? (i.n.c) are not so much advanced as in the last instance, but 

 the eth mo-palatines are larger. 



The suspensorium, besides being more out-turned, has sent forth a small pterygoid 

 tongue of cartilage {e.pg) ; but this shows at present so little affinity for the bony plate 

 beneath it that it crosses it at a right angle. The cartilaginous process has at present 

 the same outward direction as the body of the suspensorium. 



The investing bones and the inferior arches had nothing in them differing from the last 

 to make them noteworthy ; tbc more pointed skull of necessity has narrower roof- and 

 floor-bones. 



Skull of larva of Spelerpes salmonea, 3| inches long. 



These larva? were much longer than the last, they were just ready for undergoing the 

 Salamandrian metamorphosis, and yielded some very interesting results. One of the 

 most important of these is the slowness of these larva? in acquiring those characters 

 which would lift them up out of the level of Proteus and Ileuobranchus. 



Large as these specimens were, I could detect no additional parts to the fore face ; they 

 were as simple there as in the types just mentioned. 



There is not much at present to remark upon in the occiput ; the cartilage above is 

 less, but it is undiminished below ; and this specimen had more notochord (fig. 6, nc) 

 than the last. 



* The account given of the columella of these Urodeles iu my "Abstract" (Linnean Society's Journal, Zoology, 

 vol. xiv. p. 719) is incorrect; it is not a " pseudo-columella ;" the facial nerve passes over it. 



