568 
ME. W. K. PAEKEE ON THE STEUCTUEE AND DEVELOPMENT 
The second basibranchial (Plate 27. fig. 7, and Plate 25. fig. 6, b.br. 2) has lost its shaft, 
and only the bony forks, with soft extremities, remain, as the V-shaped thyro-hyal, now 
part of the laryngeal apparatus. 
It is easy to harmonize this hyo-branchial structure with the so-called hyoid of a Bird. 
The symmetrical cartilages that form the skeleton of its tongue are hypo-hyals that 
unite and partly ossify; the so-called basihyal of the Bird answers to the first basi- 
branchial of the Newt, and the hinder piece is the second basibranchial. The long 
cornua of the Bird are the moieties of the first branchial arch — epi- and cerato- 
branchials (“ Fowl’s Skull,” plate 87. fig. 11). 
I think that the stages of this single type will be considered very instructive by all 
whose pleasure it is to work out the morphology of the skull ; to me it seems to be a 
lamp giving light to all around. 
For want of space I am only able to give the lesser part of my researches into the 
structure and development of the Urodelous skull ; but to add to the supposed value of 
the account of the type above given, I am anxious to describe the lowest kind of adult 
skull, that of Proteus anguinus, and that of one of the highest, namely, Seironata ( Sala - 
mandrina) perspicillata. 
The larva of the latter has yielded some important conditions of the ground-plan of 
the skull, and these will be also described. 
Skull of the adult Proteus anguinus. 
The simple skull of this the lowest known Perennibranchiate Urodele is in a general 
way comparable to that of small larvae of Siredon ; but whilst in some things it is com- 
parable even to the second stage, just described, in others it has to be compared with 
the largest gill-bearing Axolotls. 
It is, however, in some respects unique, and in others only comparable to the most 
generalized and ichthyic of the group ; the difference between its skull and that of the 
Caducibranch next to be described (compare Plates 28 & 29) is immense. 
The half-ossified chondrocranium (Plate 28. figs. 1, 4, 5), simple as it looks, is not in 
a primitive condition; certain tracts of cartilage have been absorbed so as to give it an 
appearance of bilateral separateness which it did not possess at first, and, on the other 
hand, bony deposit has in some places bridged over tracts that were always scant of 
cartilage. 
The fewness of the investing bones is very instructive, — just a few more than we find 
on the chondrocranium of the Lepidosiren ; and these are those that appear first in the 
larvae of the higher kinds of Urodeles. 
Yet this skull-building would have been but half complete if these “ shingles ” had 
not been superadded ; for here there is no such free growth of cartilage as is seen in 
those types (the Selachians) whose dermal bones retain their independence, and show 
no affinity for the skull. 
But few as these subcutaneous hard tracts are, they are brought completely under 
