SHUFELDT.] OSTEOLOGY OF THE TETRAONID. 665 
men, cordate in outline above, elliptical below, between them, giving 
passage to the fibres of the temporal muscle that is markedly charac- 
teristic of the Tetraonide. Below the point of union this sphenotic 
process, as this latter apophysis has been termed by authors, is triangu- 
lar, with its apex pointing forwards and downwards, flat, with its inner 
surface looking forwards, upwards, and inwards. Internally, the alis- 
phenoid is deeply concave. (Plate VI, Fig. 52, and other skulls illus- 
trating this paper.) 
The external appearance of the mastcid! is well shown in Plate V, Fig. 
50, and as m. s., Fig. 51. Internally the half-cells observed close in by 
the aid of similar excavations in the segments of the occipital vertebra, 
the acoustic capsule; and a double-concave surface assists in forming 
cranial fosse. 
We now come to examine the ornithic characters of one of the most 
interesting segments of the bird-skull, the centrum of the parietal 
vertebra, well termed by most ornithotomists and general anatomists as 
the basi-sphenoid. At an early, date in the life of the chick (Centrocer- 
cus and others) this bone becomes confluent with the centrum of the 
frontal vertebra be- 
yond; this conflu- 
ence takes place, if 
we may be allowed 
to differ with such 
high authority as 
Owen, who makes 
the rather sweeping 
assertion ‘“‘that the 
pit for the pituitary 
body marks the= 
boundary” (Comp. 
Anat. and Phys. of 
the Vert., vol. ii. p. Cupidonia cupido. ; 
45) in the following manner, and the sutural trace is yet discernible in 
young birds of the Family under discussion (Plate V, Fig. 51). The 
pre-sphenoid lies beneath a tuberous process projecting anteriorly from 
the latter bone, reaching nearly as far back as the carotid foramina. 
The combined bones, the centra of the two mid-cranial vertebra, thus’ 
constitute the compound bone basi-pre-sphenoid of comparative anato- 
mists. 
Viewed from above, we discover, proceeding from before backwards, 
in the median line, 1. The upper aspect of the apophysis just mentioned, 
and immediately to its rear che deep “sella turcica” with the osseous 
canals of the carotids opening into one foramen at its base; 2. Two 
smooth surfaces, one on either side and a little laterally, for the optic 
chiasma to rest upon; 3. Another surface still more posteriorly for the 
mesencephalic fossa, being perforated by diminutive parial foramina; 
4. A roughened open space for the articulation, with the head of the 
wedge-like basi-occipital. Auteriorly, and at the same time laterally, 
broad and uneven borders for the alisphenoids, with their smooth groove- 
lets of the foramen ovale, while back of these again, on either posterior 
angle, a concave wing-like expansion, the terminations of the Kustachian 
'The bone here called mastoid is the squamosal of the majority of authors, as Huxley, 
Parker, and others. It corresponds with the bone that bears the same name in the 
works of Professor Owen. The bone squamosal of this latter author, and used in the 
same connection by myself in this monograph, is the quadrato-jugal of Huxley and 
others. 
