1903. ] OSTEOLOGY OF THE CUCULIFORMES. 265 
the metencephalic fossa, midway between the sella turcica and the 
floccular fossa, and is overhung by a sharp ledge formed by the 
inferior border of the metencephalic fossa. 
The pituitary fossa is large, deep, and tubular. The hinder 
border of the fossa—the dorswm selle—forms a tumid lip. 
Anteriorly the fossa is bounded by the pre-pituitary ridge, which 
forms a broad triangular optic platform. This platform 1s carried 
far forward into the interorbital septum, rising gently in its 
course, and then turning abruptly backwards to terminate at the 
pre-optic vidge, which may be traced into the tentorial ridge. 
The form of the optic platform contrasts strongly with that in 
some other types, ¢. g. Accipitres. The tentorial ridge in the 
region of the pre-optic platform is but feebly developed. On the 
parietal wall, however, it becomes tolerably distinct, especially in 
Geococeyx and the Musophagi. In these, on its way to the median 
falx it meets, near the crest of the epiotic, the sharply-defined 
internal border of the mesencephalic fossa, and forms therewith 
a prominent angular boss of bone, especially well marked in 
Geococeye. The bony falx is not very strongly developed. 
The oculo-motor (iii.) and abducens (vi.) nerves leave by a 
common aperture, forming a deep groove across the posterior 
angles of the optic platform. 
The cerebral fosse lie quite in front of the cerebellar fossa, and 
ave more flattened dorso-ventrally in the Cuculi than in the 
Musophagi. 
The olfactory fosse axe relatively feebly developed. 
The Premacilla. 
The external, as distinguished from the palatal, portion of the 
upper jaw is made up mainly by the premaxilla. This region of 
the jaw, in the Cuculiand Musophagi, varies considerably in form. 
Normally, it may be described as about as long as the cranium. 
In Crotophaga it is slightly longer than this, im Geococeyx and 
Saurothera very much so. Typically, it may be described as 
hemicrescentic in outline, depressed from above downwards, and 
tapering from the base forwards. In Geococcyx and Saurothera 
it is long and pointed; in Crotophaga surmounted by a sharp, 
high keel; in the Musophagi more or less inflated. 
The premaxillary portion of the jaw is slightly decurved at the 
tip, and the palatal surface is level with the culmen. The nasal 
processes of the premaxilla fuse completely with the nasals. 
A nasal hinge oceurs in Z’uracus among the Musophagi, but is 
wanting in the Cucull. 
The Mawxillo-jugal Arch. 
The maxilla is indistinguishably fused with the premaxilla. 
The maxillo-palatine processes are expanded horizontally, and 
meeting the ventral border of the nasal septum in the middle line, 
form an indirectly desmognathous palate. 
