OF THE SKULL IN THE URODELOUS AMPHIBIA. 
553 
If we compare this with the foregoing stages it will be seen that the great basal 
fontanelle has become twice as long (in proportion to its breadth) as it was at first. 
Its high walls, inbent both above and below, are still unossified ; the cross wall (inter- 
nasal plate) has become a thick mass of cartilage, through the sides of which the 
olfactory nerves pass obliquely. 
The lateral parts now show their morphological meaning clearly ; large hollow, 
cartilaginous crescents cover the inner and posterior regions of the nasal sacs, and the 
flabelliform trabecular cornua floor the nostrils and form a curved model on which the 
premaxillaries and maxillaries are grown (Plate 24. figs. 1-3, px., mx., na., c.tr.). 
In the notch formed by their posterior margin, the internal nostrils appear surrounded 
by a frame of fibrous tissue and mucous membrane. The primary independence of the 
curved flap of cartilage behind the simple nasal roof is here well shown (Plate 24. 
figs. 1, 3, e.pa.) ; it is neither part of the nasal roof nor a mere outgrowth of the trabe- 
cular wall : it may coalesce with both, as in Triton cristatus. 
The forward curve of the antorbital is caused by this tendency ; it follows the curve 
of the nasal roof, drawn to it as a tendril is drawn to some stout stem. For in the 
Selachians it generally runs backwards (Gegenbaue, op. tit.), and it does in Proteus 
(Plate 28 ) ; but in the Batrachia it grows both ways, and is like the letter T, the stem 
running inward and upward. 
But the part which I have lately called “ ethmo-, pre-, and post-palatine ” in Bitfo 
vulgaris (Phil. Trans. 1876, part 2, plate 54. figs. 3, 4) in its posterior crus is most pro- 
bably continuous with another facial cartilage, represented in Siredon by a distinct piece 
or element (Plate 24. figs. 1-3 ,pt.pa.). 
This element, which may be called the “ postpalatine,” is new to me in these low 
types, this species and this stage having alone yielded it ; it is a short flat bar, rounded 
at both ends, and lying obliquely upon the narrowest part of the pterygo-palatine bone, 
a little behind the antorbital, and having a similar outward and forward direction. 
This cartilage is attached by fibrous tissue to the fore part of the pterygoid outgrowth 
of the suspensorium — the “ symplectic ” process of the mandibular pier. 
A transpalatine cartilage has long been familiar to me in the palate of Passerine 
Birds (see Monthly Micr. Journ. 1873, plates viii.-x. “Turdidse,” plates xxxiv.-xxxix. 
“Corvidae, ” and plates ii.-xi. “Paridge;” Trans. Zool. Soc. vol. ix. part 5, Dec. 1875, 
plate lv. Corvus and Ruticilla ; and Trans. Linn. Soc. ser. 2, Zool. vol. i. plate xxi 
lAnota and Troglodytes). 
This ornithic palatine element, like its counterpart in Siredon, belongs to the anterior 
sphenoidal region, and therefore comes next in front of the mandibular arch, whose 
suspensory relation is to the posterior sphenoid. 
In the Bird this cartilage soon becomes ossified, endosteally, and then rapidly coalesces 
with a bone (the main palatine) which runs from the front of the pterygoid to the side 
of the prenasal rostrum. Along these regions, then, in Siredon it soon coalesces with the 
mdccclxxvii. 4 i 
