876 SAGO LL: 
of smaller foramina for the exit of the Ist branch of the nerv. 
trigeminus and of the 3rd, 4th and 6th Cranial Nerves. Frequently, 
however, one or more of these leave the cranial cavity together 
with the optic nerve, converting in such cases the optic foramen 
into a foramen Jlacerwi anterius. The olfactory or Ist pair of 
cranial nerves leave the cranial cavity at the point where the 
Orbitosphenoid meets the Frontal, and reach the nasal cavities 
by passing above the interorbital septum. 
The Frontals form the greater portion of the upper surface of 
the Skull, and by their forward, lateral or backward expansion 
come into contact with a great number of bones, such as the 
Parietals, Squamosal and Opisthotic, Ali-orbitosphenoid, Ethmoid, 
Lacrymal and Nasal, Maxillary and Premaxillary. In most em- 
bryos the Frontals and Nasals are originally separated by the 
upper portion of the Ethmoid, which appears on the surface, and 
this condition is persistent in Struthio; but otherwise the Ethmoid 
is overlaid by expanding growths of the Pramaxille and the Nasals 
until these reach the Frontals. Posteriorly the Frontals combine 
with the Squamosal and Alisphenoid in forming the postorbital 
process ; and, as this part often ossifies from a separate centre, it 
possibly represents the postfrontal of other Vertebrates. The space 
between the Frontal, Orbitcsphenoid and Ethmoid is filled by the 
Lacrymal, which always forms part of the anterior border of the 
orbit (processus orbitalis anterior), and has a perforation through 
which pass the secretions of the lacrymal and various orbital glands. 
The Lacrymal exhibits many modifications which seem to be of some 
taxonomic value: most generally it fuses with the Frontal and 
Nasal, but it may fuse with the former and articulate with the 
latter, or vice versa as in Vanellus; or it may articulate with both as 
in Ardea, or may fuse with the much-expanded Maxilla, as in 
Balxniceps and Podargus; or it may fuse with the Ethmoid as in 
Corvus coraz, or again may articulate with the Palatal as in 
Struthio, or with the Jugal as in Corvus, Psittaci and Accipitres. 
Many birds, as most Accipitres, several Callinv, beside Grus and 
Struthio, possess Supraorbital bones which are loosely attached, one 
or more on either side, to the posterior margin of the Lacrymal and 
the adjoining side of the Frontal. 'To the same category as these 
belong the Infraorbitals, which join the Jugal or downward process 
of the Lacrymal, and protect the lower side of the eyeball. 
The Nasals, which are always conspicuous, send out three 
processes—(1) a preemaxillary which joins laterally the posterior 
dorsal praeemaxillary process and forms the upper margin of the 
nasal cavity, (2) a lateral one, descending and joining the Maxilla 
so as to border the nasal cavity behind, and (3) a frontal process 
which, uniting with its fellow on the other side, overlaps the upper 
surface of the Ethmoid and frequently fuses with the anterior 
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