220 



basioccipital opens, transmitting the lateral dorsal aorta; while in my 

 larval specimen the aortal canal opens immediately posterior to the 

 canal in the ascending process of the parasphenoid. Running forward 

 in this canal in the parasphenoid, and accompanied by a lymph vessel 

 and a small nerve, doubtless sympathetic, as Pollard has suggested, 

 the carotid reaches the anterior edge of the ascending process of the 

 parasphenoid and there passes ventral to the trigeminus portion of a 

 perfectly typical trigemino-facialis chamber. This trigeminus portion 

 of the chamber lies in an excavation on the outer surface of the 

 chondrocranium, but the chamber is continued posteriorly, as far as 

 the foramen for the radix facialis, by a closed canal in the cartilagi- 

 nous wall of the cranium, and then, beyond that point, to the opening 



Diagrammatic representation of the prebranchial arteries in Polypterus senegalus. 

 7, II First and second branchial arches, ahy afferent hyoideau artery. eJiy efferent 

 hyoidean artery, emd efferent mandibular artery, ec external carotid artery, ic internal 

 carotid artery, cer cerebral artery, on orbito-nasal artery, da dorsal aorta. 



that Traquair describes as the exit of the facial nerve, by a canal 

 that lies between the excavated side wall of the chondrocranium and 

 the ascending process of the parasphenoid. When the carotid, running 

 forward, reaches the hind edge of the trigeminus portion of this tri- 

 gemino-facialis chamber, it separates into its external and internal 

 branches. The external carotid runs upward into the trigemino-facialis 

 chamber. The internal carotid remains below in the canal in the para- 

 sphenoid, where it is joined by a branch of the jugular vein which 

 comes down from the trigemino-facialis chamber, and by a nerve which 

 is doubtless the palatinus facialis, as Pollard has stated, though I 

 have not as yet attempted to identify it. The branch of the jugular 



