300. MR. W. K. PARKER ON THE OSTEOLOGY OF BALZNICEPS REX. 
the Adjutant, the Heron, the Rook, the Goatsucker (Caprimulgus), the Swift (Cypselus), 
and in various other birds, developed as a distinct centre of bone in the cranio-facial 
axis. The posterior osseous centre has already been described as the pre-sphenoid ; 
the anterior element (which in a large number of birds consists principally of persistent 
cartilage, with a membranous space between it and its successor, the pre-sphenoid) is 
the true ethmoid, the catacentric centrum of the ethmoidal sclerotome (Goodsir, 
op. cit. p. 143). Cuvier called the posterior piece the ‘ ethmoide.’ It is evident that 
the axial parts of two cinctures, one of the cranium and the other of the face of the 
Struthionide, have been considered to belong merely to one segment of the skull. But 
evidence is not wanting to show that the large axial mass of bone figured 14 by Professor 
Owen (Rep. on Archet. fig. 8. p. 190) is developed even in the aberrant Brevipennes 
from an anterior and a posterior osseous centre. Many years ago we dissected and 
figured the cranio-facial axis of an Emeu (Dromaius ater) only six weeks old, in which 
the orbito-sphenoidal region, the antorbitals, and the anterior part of the so-called ‘ pre- 
frontal mass’ were still cartilaginous. The flat-topped pieces, however (the anterior of 
which props up the ‘nasals,’ the posterior forming the buttress of the sphenoido- 
frontals), formed one V-shaped piece of bone, the upper portions being quite distinct, 
whilst the flat descending plates had evidently coalesced; for ossification commences, 
not at the point where these pieces had become confluent, but just below the horizontal 
outspread upper part, where, in this young Emeu, they were still widely distinct. 
Looking at the lower part of the great fronto-maxillary hinge in the Balzeniceps, we 
see, between the incurved plates of the lacrymals, a large mass of thinly-coated spongy 
bone, which forms the posterior part of the axis of the greatly-developed face. This 
broad-topped mass of bone acts as a buttress to the nasal processes of the pre-maxillaries 
and to the nasals, besides forming a large and important part of the ‘ great hinge,’ and 
articulating with its immediate successor the pre-sphenoid below the hinge, thus adding 
strength to the junction of the roof-bones. This is the true ‘ ethmoid’ ; at least, itis the 
homologue of the mesial part of the human ethmoid, the out-standing process of which 
is called the ‘ crista-galli,’, This centrum of the face of Balzniceps is as well developed 
as its cranial successor the pre-sphenoid ; and the posterior aspect of the former is so 
much like the anterior aspect of the latter, that it seems like an illusion, and as though 
a mirror had given us a backward reflexion of the front of the pre-sphenoid. 
The posterior face of the ethmcid of Baleniceps is sharply carinate for about two- 
thirds of its depth, the keel ceasing and a groove commencing opposite the projecting 
end of the basi-sphenoid. This groove, very shallow at first, runs downwards until it 
loses itself between the spur-shaped posterior processes of the ethmoidal pterapophyses 
in the mesial palatal groove. Where the keel ends, there the ethmoid, the centrum of 
this sclerotome, has coalesced with its low-lying pterapophyses. The mass of the 
ethmoid a few lines in front of the keel is much thicker than that of the pre-sphenoid ; 
but the external bony table begins soon to be deficient on each side, and all trace of 
