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The ventral edge of this ventral portion of the proötic is overlapped externallv by the lateral 

 edge of the body of the parasphenoid, its anterior edge being in part overlapped externally by, and 

 in part suturating with the hind edge of the ascending process of the same bone. In the angle between 

 the ascending process and the body of the parasphenoid, between that bone and the proötic, is the 

 internal carotid foramen, which leads froin the external surface of the skull inward and forward 

 between the parasphenoid and the proötic, and then across the internal carotid incisure, into the 

 invodome. On the external surface of the proötic, and running from the dorsal edge of the internal 

 carotid foramen upward and backward toward the facialis opening of the trigemino-facialis Chamber, 

 there is a slight groove which marks the course of the internal carotid artery before it enters the 

 foramen. Immediately anterior to this groove, on the lateral surface of the ascending process of 

 the parasphenoid, the infrapharyngobranchial of the first branchial arch is flexibly attached by strong 

 fibrous tissues. 



The mesial process of the proötic forms, as usual, part of the roof of the myodome and part 

 of the floor of the cranial cavity. The angle between it and the ventral part of the bone forms the 

 dorso-lateral angle of the myodome, and in this angle, near its anterior end, there is a deep pit leading 

 upward in the bone almost to the floor of the trigemino-facialis Chamber; a remnant, doubtless, of 

 the passage which, in Amia, connects the ventral portion of the myodome with its upper lateral 

 Chamber. Immediately anterior to this pit is the ventral opening of the canal for the palatinus fac- 

 ialis, that canal beginning on the cerebral surface of the bone, in what has already been referred 

 to as the trigemino-facialis recess. The canal lies wholly in a part of the bone that is of meni- 

 branous origin, as will be later explained. 



The dorso-lateral angle of the myodome is well rounded, and is continued forward upward 

 and laterally to the internal jugular notch, where, turning backward, it falls into and is continuous 

 with the anterior end of the internal jugular groove. The internal jugular notch, as already fully 

 described when describing the alisphenoid, lies between the dorsal end of the ascending process of 

 the parasphenoid and the ventral, process-like end of the anterior one of the two little ridges on 

 the external surface of the alisphenoid, and the internal jugular groove, beginning there, runs back- 

 ward and lateraUy along the orbital surface of the proötic into the ventral end of the trigeminus 

 opening of the trigemino-facialis Chamber. The slight ridge on the proötic that forms the ventral 

 edge of the groove is closely applied, in its anterior portion, to the inner surface of the dorsal edge 

 of the ascending process of the parasphenoid, while posteriorly it is continuous with the anterior 

 edge of the lateral wall of the trigemino-facialis Chamber. In the dorso-lateral angle of the orbital 

 opening of the myodome, immediately mesial to the internal jugular notch, is the external opening 

 of the oculomotorius foramen, that foramen lying wholly in the proötic. Dorsal to the internal jugular 

 groove, on the orbital surface of the proötic, there is often a slight ridge with a process-like and down- 

 wardly projecting ventral end, exactly similar to the two ridges on the alisphenoid. The process- 

 like end of this proötic ridge is, like the processes on the alisphenoid, connected by fibrous tissue 

 with the dorsal edge of the ascending process of the parasphenoid, the process and tissue evidently 

 representing an anterior cxtension of the lateral bounding wall of the trigemino-facialis Chamber. 



In Amia the lateral bounding wall of the trigemino-facialis Chamber is well developed, being 

 wholly of bone or cartilage, while the mesial wall is wholly of membrane. In Scorpaena, and also 

 in Scomber, it is the mesial wall that is well developed, the outer wall being greatly reduced, while 

 Lepidosteus presents a condition intermediate between Amia and Scorpaena. 



