ARTICULATION OF PALATOQUADRATE IN CCELACANTHIDS. 41 



5. The Postorbital Articulation of the Pahitoquadrate with 

 the Neurocranium in the Coelacanthid Fishes. Bv 

 Edwakd Phelps Allis, Jr., F.Z.S. 



[Received October 25, 1922 : Read February 6, 1923.] 



In a recent work (Allis, 1922), I came to the conclusion that 

 the postorbital articulation of the palatoquadrate with the neuro- 

 cranium in Wimania and Axelia, two of tlie Ccelacanthidte, was 

 homologous with that in the recent Hexanchus and Heptanchus, 

 and not with that in Lepidosteus. This conclusion was based 

 largely on my assumption that the vena jugularis of these fishes 

 ran posteriorly between the articular process of the palatoquadrate 

 and the cranial wall, instead of accompanying the ramus 

 ophthalmicus lateralis, as suggested by Stensio (1921), and 

 traversing, with that nerve, a foramen that lay between the 

 alisphenoid and basisphenoid bones of the latter author's 

 descriptions. Further consideration of the subject, in connection 

 with a later work by Stensio (1922), has led me to conclude that 

 the vein did not have the course ascribed to it by either Stensio 

 or myself, but, accompanying the ramus ophthalmicus profundus, 

 traversed a foramen that lay anterior, instead of posterior, to the 

 alisphenoid, and so entered a trigemino-facialis chamber iii the 

 cranial wall. This conclusion modifies radically my conception 

 of the conditions in these fossil fishes, but I, nevertheless, still 

 think that the articulation of the metapterygoid Avith the cranium 

 was of the type found in the recent Hexanchus and Heptanchits, 

 and not of that in Lepidosteus. 



There are, in recent fishes, two processes of the palatoquadrate 

 that are here concerned, as well as two processes of the neuro- 

 cranium. One of the processes of the palatoquadrate is the 

 processus basalis, or pedicle, and the other the processus 

 metapterygoideus, and both of them are found in typical condition 

 in the adult Amia. The processus basalis of this fish forms the 

 dorso-anterior coi'ner of the metapterygoid, and lies in the plane 

 of the body of the palatoquadrate. It is directed toward the 

 lateral edge of the basis cranii, in the region of the orbital 

 opening of the myodome, and is there connected with it by a band 

 of connective tissue. The floor of the orbital opening of the 

 myodome is the homologue of the processus basipterygoideus of 

 the Sauria (Allis, 1913), and it is lined ventrally, and supported, 

 by the anterior portion of the ascending process of the 

 parasphenoid. The processus metapterygoideus projects dorso- 

 mesially from the external surface of the metapterygoid, is 

 directed toAvard the projecting dorso-lateral corner of the 

 postorbital process of the neurocranium, and connected with that 

 process by a membrane that covers the external surface of the 



