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XV. On the Structure and Development of the Shull in the TJrodelous Amphibia. — Part I. 
By William Kitchen Parker, F.R.S. 
Received November 9, — Read November 23, 1876. 
[Plates 21 - 29 .] 
Introductory Remarks. 
Before submitting to the Royal Society a third paper on the Skull of the Batrachia, it 
would seem to be better for me to bring forward the results of my work on one of the 
simpler kinds of Amphibia, namely the Axolotl, a type belonging to the “ Urodela.” 
Through the kindness of friends * I have been enabled to follow the Axolotl through 
many stages, and several other types have been worked out both in their larval and 
adult stages ; some of these fill up lacunae in the series of Axolotls. 
That type, however, is here given in nine larval stages, besides the Amblystoma stage 
into which certain individuals pass. 
Ten or twelve stages are not at all more than are needed for following up and catching 
every important modification in the skull of a Vertebrate no higher than a Salamander 
— a type which, practically, stands between the “ Pisces Dipnoi ” and the true Reptiles. 
Moreover this leaves a large fore margin to the embryologist proper, whose most 
important work dovetails into mine where mine begins. 
To the morphologist the group of the Urodela is of great interest, first in its relations 
to the Batrachia, the Csecilians, and the extinct Labyrinthodonts, and then to the more 
generalized Fishes below and the Reptiles above. 
And not only with the Reptiles, for the more reptilian types of Birds, such as the 
Dinornis, the Emu, and the Cassowary, have skulls that are easily interpreted by one 
who is familiar with the Salamandrian skull. 
But perhaps the most instructive comparisons are those which may be made of the 
skull (chondrocranium) of the tailed Amphibia with that of the Elasmobranch Fishes ; 
and, besides my own researches into the development of the skull in Baia and Scyllium 
(now being published), I gladly avail myself of the labours of Professors Gegkenbaur 
and Huxley in that and related groups f. 
* In these researches I have been most liberally supplied with materials by the undernamed scientific friends, 
namely — Messrs. Alex. Agassiz, Flower, Gunther, Mjvart, Muhie, and, above all, Tegetmeier ; my specimen 
of Proteus anguinus belonged to the late Henry Christy, Esq., F.R.S., and was given me by his brother, 
Edmund Christy, Esq. 
t The work of the former of these excellent authors here referred to is his ‘ Untersuchungen zur verglei- 
MDCCCLXXVII. 4 F 
