52 MR. E. P. ALLIS ON POSTORBITAL ARTICULATION OF 



mai'ked resemblance to the conditions in the Selachii. Stensio 

 says (1921, p. 73) that there was a large mandibula in Wimania 

 (and hence probably in the other two fishes also), and that this 

 presupposes a powerful adductor muscle. Comparison with 

 recent fishes would then indicate that the surface of origin of 

 this muscle on the palatoquadrate must have extended upward 

 at least to the dorsal edge of the metapterygoid, and Stensio 

 considers it probable that the muscle extended beyond that edge 

 and had its origin in part on the lateral surface of the neuro- 

 cranium. The levator ai"cus palatini, if present, would then 

 necessarily have had its insertion, as in Heptanchus and Hexcin- 

 chus, either along the dorsal edge of the metapterygoid or partly 

 on that edge and partly on its mesial surface. 



On the internal surface of the palatoquadrate there is a large 

 dermal pterygoid bone, and a process of this bone extends to, or 

 neai-ly to, the point of the dorso-anterior process of the meta- 

 pterygoid, thus supporting that process. The dorso-posterior 

 process of the metapterygoid, on the contrary, extends consider- 

 ably beyond the dorsal edge of the pterygoid, this leaving a 

 considei-able portion of the internal surface of the metapterj^goid 

 exposed beyond the pterygoid. On the lateral surface of the 

 pterygoid there is a strongly pronounced and rounded ridge 

 which extends upward to the point of the dorso-anterior process 

 of the metapterygoid, and strongly suggests that that point 

 represents the dorsal end of some element of the mandibular 

 arch. 



The relations of the two processes on the dorsal edge of the 

 metapterygoid to each other, to the palatoquadrate, to the 

 pterygoid, and to the muscles of the arch, thus all strongly 

 suggest that the posterior one is a processus metapterygoideus, 

 and the anterior one either the entire processus basalis or the 

 anterior end of a ridge-like process similar to that in the Selachii, 

 the posterior portion of the ridge lying along the internal surface 

 of the palatoquadrate. There was quite probably a spiracular 

 canal in these fishes, as there is in the recent Polypterus^ and 

 not simply a diverticulum of that canal, such as is found in the 

 recent Holostei and Teleostei ; and, where this canal is pi-esent, 

 there is, in recent fishes, no articulation of the processus basalis 

 with the neurocranium. 



There is thus strong presumptive evidence that, in these fishes, 

 it is a processus metapterygoideus that articulates with the 

 cranium, and, in recent fishes, this process never articulates with, 

 or even approaches, a processus basipterygoideus. This is 

 evidently in favour of the assumption that the process e is a pro- 

 cessus postorbitalis, and the relations to it of the cranial nerves is 

 also in favour of this interpretation. 



There is, in Wimania and Axelia, a median bone which, as 

 already stated, Stensio considers to be a basisphenoid, and it is 

 said by him to consist of a body (corpus), and three processes on 

 either side, one of these processes being dorsal, one anterior, and 



