2 MARY L. WALKER ON THE FORM OF 
and which is here (as in most cases) divided by a deep groove [capitular groove] into 
an internal capitulum (hw.) for articulation with the prootic, and an eaternal (h.e.) 
for articulation with the squamosal; the shaft of the bone, leading from the head 
to the distal extremity, which forms the complicated articular surface for the 
mandible ; an anterior process, the metapterygoid process of PARKER (a.p.), pro- 
jecting forwards and inwards from the shaft towards the orbit; a smaller process 
below and to the inner side of this last, which articulates with the pterygoid bone, 
and which we may call the pterygoid condyle (p.c.): to it a ridge is directed on the 
inner surface of the bone, descending from the neighbourhood of the capitular groove ; 
an articular surface at the base of the shaft, on its outer aspect close above the 
mandibular articulation, for the quadrato-jugal: this articular surface is usually 
hollowed and cup-like, and may be called the quadratoyugal cup (qyj.c.). The 
articular surface for the mandible is very complicated and variable: in the present 
case it is divided into two parts, a prominent rounded anterior articular surface or 
condyle (a.a.), and a posterior articular surface transversely elongated, and. trochlear 
in character, presenting an internal (p.e.) and external (p.a.) condyle, separated 
by the trochlear groove. The view from below shows also a tract of bone projecting 
behind the external condyle, which in certain cases becomes more conspicuous. 
Of these points those most liable to variation are: the greater or less separation 
of the two capitula; the form of the anterior process; the presence or absence of 
the pterygoid condyle; the greater or less’ completeness of the quadrato-jugal cup ; 
and the whole form and character of the mandibular articulation. 
THE Ratitaz. 
The quadrate of the Ratitee has been pretty fully dealt with by Parker in his 
memoir on the Skull of the Ostrich. For this reason, and for the better one that 
we do not yet possess a full series of Ratite skulls, we figure it in one form only, the 
Fig. 2. REA AMERICANA. 
Rhea. In its clumsy form this quadrate differs from all the others that we shall 
hereafter describe. The head is very imperfectly divided into two capitula. The 
anterior process is short, thick, and truncated ; the quadrato-jugal cup is imperfect, 
and is represented merely by an irregular crescentic hollow, the lower part of the 
cup being absent. The pterygoid condyle is not defined, being merged in a great 
