NO. 4 AN ENDOCRANIAL CAST — GAZIN 7 



above the position of the foramen ovale and nearer the acute angle 

 between the faces of the petrosal fossa is a small flattened prominence 

 which is the filling of the hiatus Fallopii through which the super- 

 ficial petrosal nerve entered the petrosal. 



Evidence may be seen on the cast of a part of the vascular system 

 which essentially surrounded the petrosal. Anterolateral to the cere- 

 bellar hemisphere the lateral sinus, at the position of emergence rep- 

 resented on the cast, divided and the lateral sinus proper turned 

 posteriorward where it is represented on the cast by a prominent shelf- 

 like ridge extending along the outer margin of the lateral lobes. It 

 then turned downward to the foramen lacerum posterius. The other 

 branch entered directly a foramen, evidently on the suture between 

 the petrosal and parietal, possibly involving the squamosal, the aque- 

 duct of Verga as used by Saban (1963), that extends slightly for- 

 ward and outward as well as downward, paralleling the lateral margin 

 of the petrosal fossa. Partway down its course, apparently in the 

 petro-squamosal suture, this duct is joined by an adjacent tube that 

 extends ventrally from the parietosquamosal foramen, permitting 

 vascular communication with the temporal fossa. Just above the outlet 

 of this system through the postglenoid foramen, the canal is joined 

 forward from within the cranial cavity by the vascular representation 

 seen on the side of the pyriform lobe of the cast at about the rhinal 

 fissure. The latter vascular sinus, as has been noted, communicated 

 forward through the cranio-orbital foramen with the orbital fossa 

 and is believed to have included the stapedial artery as well as veins. 



A conspicuous ridge on the cast extending anteromedially from the 

 position of the foramen lacerum posterius is seen from the bone to 

 occupy a canal along the suture between the basioccipital and petrosal 

 to near the fossa for the hypophysis. This is no doubt the inferior 

 petrosal sinus. A very short distance anteromedially along this ridge 

 of the cast is an indistinct rise which represents an aperture much 

 better observed on the bone. It corresponds to the forward opening 

 of a canal following the suture between the basioccipital and petrosal 

 or bulla (in part). It opens posteriorly adjacent and medial to the 

 foramen lacerum posterius, and anterior or anteromedially adjacent to 

 the condylar foramen (see Gazin, 1958, pi. 3, fig. 2). This is almost 

 surely the foramen "Fx" in Hiirzeler's figures of Necrolemur (1948, 

 figs. 27 and 28). I suspect that it served to unite a part of the venus 

 system at the inferior petrosal sinus to the sinus of the vertebral 

 column through the condylar foramen and foramen magnum. It 

 corresponds to the larger and more importantly developed canal in 



