5i MR. H, P. ALLIS ON POSTORBITAL ARTlCULATIOif Of 



in Wimanici posterior also to the dorsal process of the basi- 

 sphenoid. The ramus ophthalmicus profundus of Axelia is said 

 to run forward internal to the base of the alisphenoid, and to 

 issue from the cranium anterior to that bone, and in Dlplocercides 

 it has similar relations to the alisphenoid wulst. In Wimania 

 it is said to probably have issued through that small canal, 

 above referred to, that traverses the anterior process of the 

 basisphenoid, but, as will later appear, it is much more probable 

 that this canal was traversed by the efierent pseudobranchial 

 artery. The ramus ophthalmicus lateralis trigemini is said to 

 run forward, in Wimania, over the dorsal process of the basi- 

 sphenoid, close to the lateral wall of the brain-case, thus 

 evidently issuing from the cranium between the dorsal process 

 and the alisphenoid, and then running forward lateral to the 

 latter bone. In Axelia this nerve lies in a groove that crosses 

 the external surface of the alisphenoid, and in Dijdocercides 

 in a canal that traverses the alisphenoid wulst and is continued 

 onward, a certain distance beyond that wulst, in the body of the 

 sphenoid bone. The vena jugularis is said to have liad, in 

 Wimania, a course similar to that of the ramus ophthalmicus 

 lateralis trigemini. In Axelia and Diplocercides its course is 

 not given. 



The profundus and trigeminus nerves of Axelia thus have, in 

 the courses ascribed to them by Stensio, exactly the relations to 

 the alisphenoid bone of that fish that the corresponding nerves 

 have, in recent fishes, to the parasphenoidal leg (pedicle) of the 

 alisphenoid, the trigeminus nerves all issuing posterior to that 

 leg and the profundus nerve anterior to it ; and as the vena 

 jugularis of recent fishes always accompanies the profundus 

 nerve in this part of its course, it seems exceedingly probable 

 that it accompanied that nerve also in Aaelia, and hence passed, 

 as in recent lishes, antero-mesial to the alisphenoid. In Diplo- 

 cercides the conditions differ from those in Axelia only in that 

 the ramus ophthalmicus lateralis trigemini traverses a canal in 

 the alisphenoid part of the sphenoid bone, instead of passing 

 lateral to it ; but even in recent fishes, as in Amia, this nerve 

 may traverse a foramen that perforates the parasphenoidal leg of 

 the alisphenoid. 



In Wimania the conditions, as described by Stensio, difler from 

 those in Axelia and Diplocercides in that the ramus ophthalmicus 

 profundus is said to have probably traversed the canal in the 

 anterior process of the basisphenoid, that tlie truncus maxillo- 

 mandibularis trigemini presumably ran outward in a notch at 

 the base of the hind edge of the dorsal process of that bone, and 

 that the vena jugularis accompanied the ramus ophthalmicus 

 lateralis trigemini, and hence passed postero-lateral instead of 

 antero-mesial, to the alisphenoid bone. This course for the latter 

 vein would be most exceptional in fishes, and it seems much 

 more probable that both it and the lumus ophthalmicus profundus 

 passed internal to the alisphenoid, as they both apparently did in 



