122 



to be wholly wanting. A deep and narrow incisure, which separates the process from the almost 

 equally tall posterior portion of the bone, transmits the internal carotid artery. From this incisure 

 a groove runs upward on the outer surface of the proötie, toward the facialis opening of the trigemino- 

 facialis Chamber, and lodges the internal carotid artery. Ventral to the internal carotid foramen 

 this groove is continued on the outer surface of the parasphenoid, but there simply marks the 

 posterior limit of the surface of Insertion of the adductor arcus palatini. The infraphaiyngobranchial 

 of the first arch has its attachment to the skull anterior to the groove, in the immediate neighbour- 

 hood of the internal carotid foramen. 



Between, or slightly anterior to the anterior edges of the ascending processes of the para- 

 sphenoid there is, in the middle line of the dorsal surface of the bone, a pronounced and sharply 

 pointed process, directed dorso-posteriorly. The anterior edge of this process is grooved, is presented 

 dorso-anteriorly, and lodges the ventral edge of the posterior portion of the cartilaginous interorbital 

 septum and, dorso-posterior to that cartilage, and continuous with it, the ventral end of the pedicle 

 of the basisphenoid. On the ventral surface of the bone, slightly anterior to this little process, there 

 is, on either side, a slight process, or ledge directed laterally, which thus has approximately the pog- 

 ition of the well developed process of Osteoglossum. 



The ORBITS are roofed by the ectethmoids and frontals, and are separated from each other 

 by an interorbital septum, the anterior portion of this septum being of cartilage, while its posterior 

 portion is of membrane. The extreme anterior end of the septum is perforated by an opening which 

 puts the orbits in communication with each other, this opening forming the median part of the anterior 

 eye-muscle canal. The hind wall of the orbit is formed by the alisphenoid, basisphenoid, proötie 

 and sphenotic, and is slightly reentrant in its lateral portion, this being due to the projecting anterior 

 edge of the lateral surface of the brain case. The ventral flange of the frontal being but slightly 

 developed, the orbital opening of the brain case is, in consequence, large and somewhat rectangular 

 in sliape. 



The MYODOME has proötie and basioccipital portions, the latter extending only about one 

 half the length of the basioccipital, and opening posteriorly on the ventral surface of that bone by 

 a small opening only. The orbital opening of the myodome is large and inclines strongly downward 

 and forward, while the roof of the proötie portion, or body of the myodome inclines strongly down- 

 ward and backward. This is due to a deepening of the orbits, posteriorly, and a correlated and marked 

 tilting upward of the mesial processes of the proötics, this giving to the myodome the appearance 

 of a large and deep recess at the hind end of the orbits. 



There is no ORBITOSPHENOID. 



The ALISPHENOID is bounded by the sphenotic, the frontal, and the prepituitary portion 

 of the mesial process of the proötie, the basisphenoid not Coming into bounding contact with it. The 

 antero-mesial edge of the bone is slightly concave, and bounds the orbital opening of the brain case. 

 This edge of the bone forms a continuous line with the anterior edge of the mesial process of the 

 proötie, and the adjoining edges of the two bones are cut away to form a rounded incisure which 

 transmits the nervus trochlearis. Dorsal to this incisure, in the anterior edge of the alisphenoid, 

 there is another incisure, often closed to form a small foramen, which transmits the cerebral brauch 

 of the orbito-nasal vein. Near the center of the bone there is a larger foramen which transmits that 

 brauch of the ophthalmicus lateralis that supplies the small latero-sensory organ in the terminal 



