OF THE SKULL IN THE UKODELOUS AMPHIBIA. 
551 
These cartilages are slightly arcuate, and have a forward turn ; they have rounded 
ends, and are broadest above : they are, as far as I have seen, universal in the Urodeles. 
Here, again, the Elasmobranchs come in to our help. I have studied their growth in 
Kays and Dogfish : Gegenbaue shows, in his invaluable memoir (‘ Untersuchungen zur 
vergleichenden Anatomie der Wirbelthiere,’ part 3, plates 1-17), that in those types the 
antorbital is sometimes continuous with the skull and sometimes distinct*. 
In Birds also we find an antorbital cartilage, which early coalesces with the antorbital 
portion of the nasal sac at its lower angle ; it chondrifies quite separately from the tra- 
becular (basicranial) bar. In Corythaix and Musophaga it might easily be taken, in its 
osseous state, for an “ os transversum ; ” but it runs across the face too far forwards, 
starting from the ethmoidal and not from the presphenoidal region. In the Passerinse 
there is a second pair of transverse cartilages, but these are in the middle part of the 
palate ; of these I shall speak in the next stage. 
As for the coalescence of the little antorbital bar with the nasal capsule, this does 
take place even in the Urodela, namely, in Salmandra maculosa and Triton cristatus. 
Another pair of cartilages are to be seen over the nasal sac ; these are the foremost 
of the “paraneural” elements of Professor Huxley (op. cit. p. 198), who, in discussion 
with me, spoke of them as upgrowths from the trabeculse. They soon coalesce with 
these bars by their lower edge ; but I have satisfied myself of their primary distinctness, 
not only in Siredon, but also in Notophthalmus viridescens in its larval state. 
These crescentic shells of cartilage have their concave edge looking forwards and 
outwards, and their convex edge looking backwards and inwards (Plate 22. figs. 6, 7, 
na.). 
We have all the essential elements here, in this stage of the Axolotl, for the morpho- 
logical development of the nasal labyrinth ; superadded parts may come in, as the bony 
plates which become correlated to or grafted upon the labyrinth ; and in many cases 
there are supplementary cartilages from the “ labial ” category, but these do not appear 
in the Urodeles. In the consolidated chondrocranium of the Selachians there is a 
notable azygous cartilage which grows forwards between the cornua trabeculse ; this is 
not seen here, but turns up in metamorphosed Salamanders (S. maculosa) ; the bar 
referred to is large in the embryo bird (the “ prenasal rostrum ”). 
Besides general increase of size there is this to be remarked now, in the mandibular 
pier, that the otic process (fig. 6, ot.p.) and the pedicle (fig. 7, pd.) are much more solid 
and massive ; the ascending process ( a.p .) is now of great breadth, especially at its line 
of union with the skull wall. The articular concavity (fig. 7, q.) is now complete. 
The chondrocranium is adding fresh bony plates in the same order in which they 
* This “lower antorbital’’ or ethmo-palatine is very common in the Carinate Birds, and I have lately described 
it in them in papers recently published in the Transactions of the Linnean and Zoological Societies ; in these 
types it is called the “ os uncinatum ” (Magnus). It is very distinct as a hooked process, both in the “ Carinatse ” 
and in the Emu and Cassowary (see “ Ostrich Skull,” plate x. fig. 18, a.i.t., and plate xiv. figs. 1 & 7, a.i.t., 
pp. 151 & 158). 
