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PROF. W. K. PARKER ON 2GITHOGNATHOUS BIRDS. Bl: 
” 
gide ;” and the nearly perfect hinge is bounded in front by a knife-like septum, as in 
Syrrhaptes, Hemipodius, and Pachyrhamphus ; but this is not ossified; it is not alate in 
the middle, but has in front two triangular lamine of bone underpropping it; the lower 
of them is a median process of the premaxillary; and the higher is the ‘ recurrent 
lamina” of the trabecul (7c. ¢); this is largely edged by unossified cartilage. 
In Thamnophilus we have a pertinent instance of the occurrence of intense ossification 
in a low type, showing that arrest of ossification is not of itself a sign of low position’. 
The whole nasal capsule is ossified, with the exception of the margin of the very large 
recurrent laminz and the septum, and had better be considered along with the vomerine 
structures. 
The alinasal turbinals (a. tb) are very large and bony, and they articulate by their 
convex end with a concavity on the horns of the enlarged vomer (fig, 9, a. tb, v). ‘The 
alinasal wall (a/.n) is not even flush with the facial bones (fig. 10), but sinks in, and is 
thoroughly ossified; below and within it is seen to have coalesced completely with the 
maxillo-palatine process (fig. 9, 7. a. 1, ma.p), and is of very small extent in the floor of 
the nose, which is here open, exposing the alinasal and inferior turbinals (a. #0, 7. th). 
Here the bony growths are much in conformity with the morphological regions, save 
that the ankylosis of the ale nasi with the palatine plate of the maxillary has produced 
a form of desmognathism. 
In Thamnophilus the vomerine moieties are as much indebted to hyaline cartilage for 
the formation of their wings and crests as in the Crow, but the source is different: here 
the cartilage is the vomerine spatula; there, in the Crow, that cartilage is soon used up, 
and then the bone grows into the nasal capsule to a certain extent. In this instance the 
vomerine cartilages are themselves large enough to form a substratum for all the out- 
growings of the vomer, so large and massive in the adult. 
Not only does the alinasal turbinal form a cup-and-ball joint with the vomer, but the 
yomer itself has an elevated subconvex facet on each side, which fits into a subconcave 
facet on the upper surface of the corresponding maxillo-palatine plate. Altogether this 
egithognathous palate is developed into a very complex kind of desmognathism. 
At first sight the septum would seem to be ossified; but a side view shows that it is 
only the inferior edge which is bony, and the bone is quite free from the cartilage; it is, 
in this state, merely a membrane bone, a “ median septo-maxillary” (fig. 8, m. s.mz). 
We shall soon meet with this element again. 
The premaxillaries form the strong, narrowish, decurved beak, and are thoroughly 
ankylosed to their surroundings. 
The pterygo-palatine arch has a typical apex, the epipterygoid hook (e¢.pq) ; it is longer 
than is usual even in the higher forms. The pterygoids are rather long, elegantly bowed, 
and have given off a large mesopterygoid, which has become ankylosed to the upper edge 
of the palatine; the pterygoids remain distinct. The palatines are extremely like those 
' Neither intense ossification nor pneumaticity of the bones are signs of “ high degree.” 
VOL. 1x.—pPart v. December, 1875, 2u 
