MR. W. K. PARKER ON THE OSTEOLOGY OF BAL/ENICEPS REX. 303 
the anterior end above, showing the long spatulate process of the primordial cranium on 
which the inter-maxillaries are moulded. The pre- or inter-maxillaries have, however, 
at this early period, much of their adult form, except that the nasal processes are short, 
and the sub-mesial palatine processes for articulation with the palatals are not yet deve- 
loped ; they may be seen three or four days later. The nasals are already ossified and 
have nearly their permanent form, overlapping the still cartilaginous pre-sphenoid 
behind, lying upon the ethmoid, and articulating below with the already ossified max- 
illaries. The spatulate ‘rostrum’ of the ethmo-vomerine cartilage is very elegant in 
birds: in the Chick it has attained its full size by the eleventh day ; at this time it may 
be seen quite uncovered beneath the two pre-maxillary centres, like a small model of the 
Spoonbill’s jaw. 
This cartilage is very transitory ; on the fourteenth day it has greatly shrunk, and by 
the nineteenth day of incubation it has become a mere thread of cartilage, being absorbed 
pari passu with the distal part of Meckel’s cartilage. In the Snake the ossific centre 
for the pre-maxillary is azygous, like the cartilage in or wpon which it is developed 
(Huxley, Croon. Lect. p. 60). In the Stickleback there are two cartilages in which the 
pre-maxillaries are developed (Croon. Lect. p. 29). ‘The malars are ossified before the 
eleventh day in the Chick. The anterior part of the ethmo-vomerine axis of birds is 
always feebly developed ; and in some birds the fibro-cartilage of which it is composed is 
deficient between the nostrils, e. g.inthe Swan. The nostrils in Crocodiles and Mammals 
are pierced in front of the pre-maxillaries (just where the bones ossify latest in the Bird), 
‘‘ whereas in the typical Lacertians, and in the extinct Plesiosaurs, Ichthyosaurs, and 
Pterodactyles, in the Ophidians, Amphibians, and Birds, they open behind these bones” 
(Goodsir, op. cit. p. 139). There is, therefore, as Professor Goodsir shows, no rhinal 
sclerotome in these latter vertebrata. In the Bird, according to Professor Goodsir, the 
vomerine sclerotome is composed of the anterior fibro-cartilaginous portion of the pri- 
mordial cranium (its catacentric centrum), and of the pre-maxillaries (its heemal arch), 
whilst the neurapophyses are absent. The ‘‘ marginal processes of the cartilaginous 
vomerine centrum extend down in front, so as to line the under- and fore-part of the 
nasal fosse, projecting somewhat behind the inter-maxillary margin of the external 
nostril. The broad projecting upper portion of the cartilaginous septum occupies the 
position of the nasal bones, while the inferior portions project from behind the inter- 
maxillaries, like opercular actinapophyses ” (Goodsir, op. cit. pp. 139, 140)’. 
The ossification of the posterior hyaline ethmoidal portion of the nasal septum is very 
varied, and takes place later than that of the pre-sphenoid. The ossified ethmo-vomerine 
axis of Balzeniceps is nearly four lines thick between the nostrils, and consists of one mass 
of bone, as is the case indeed in most birds when these parts are ossified. In the Heron 
and Adjutant, only the flat upper surface of the ethmo-vomerine cartilage is ossified ; in 
the Rook the ethmoid is knife-like, but small in longitudinal extent, whilst there are 
2 We think, with Professor Huxley, that the whole of this subject requires to be tested by the patient study 
of development, and that the existence of this vomerine sclerotome is very doubtful. 
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