STEUCTURE OF THE SKULL IN THE U110DEL0F3 AMPHIBIA. 7l7 



On the Structure and Development of the Skull in the Urodelous 

 Amphibia. By W. K. Paeker, F.R.S., P.L.S., &c. 



[Abstract.] 



In a paper which has recently appeared in the ' Philosophical 

 Transactions ' (1877, part ii. pis. xxi.-xxix. pp. 529-597), I have 

 laid down the foundations of the work of which the present com- 

 munication is intended to be a piece of side wall. In that initial 

 part the development of the skull of the Axolotl is traced through 

 nine stages, from the unhatched embryo to lax'ge specimens that 

 were losing their gills. 



Then this series was perfected by the addition of the skull of 

 Amhlystoma — one of the Salamandrians into which a Siredon-\a,v\a, 

 is very apt to transform itself. But as Amhlystoma does not show 

 the fullest type of the skull of a " Caducibranch," I have therein 

 added an account of that of Seironota perspicillafa, a small kind of 

 Newt of a high type. A small larva of that species served excel- 

 lently as an intercalary stage between the third and fourth of the 

 series of Axolotls : that, also, is added to the paper. 



But, as is well known, the lowest " Perennibranchs " (such as 

 Frofeus and Menolranchus) are but a sort of ametaboloxis larva as 

 compared with the adults of the higher kinds, and have their true 

 morphological counterparts in the early larval stage of the highest 

 kinds. These things being so, I thought it well to add an account 

 of the skull of an adult Proteus to that paper. 



The present paper (the materials for which I am indebted to my 

 kind friends, Prof. Mivart and Mr. Tegetmeir) is simply a conti- 

 nuation of the one just spoken of. It does not exhaust my mate- 

 rials, much less the subject : it may therefore be considered as 

 Part I. I have here given an account of the skull in several kinds : 

 some only in the adult condition, but others with one or more 

 larval stages. 



The first type treated is the common Spotted Salamander {Sa- 

 Jamandra maculosa), a viviparous species. Of this kind I have 

 worked out embryos wdth large branchiae, three-fourths ripe, ripe 

 cryptohranch embryos, and the adult. 



Then comes another good typical Caducibranch, namely, 

 Notophthalmus virideseiis ; of this kind I had small larvae and the 

 adult. 



