ON CERTAIN CROSSOPTERYGIANS. 1261 



forms <a postero-ventraj. process from the fronto-dermosphenotic, 

 there runs an antero-caudal sulcus, which certainly corresponds 

 to the canal for the n. ophthalmicus lateralis in Dlplocer aides. 

 These facts and the conditions in general in Axella show that 

 the trigeminus branches (with the exception of the r. ophthal- 

 micus profundus), the lateralis nerves accompanying them, and 

 the vena jugularis ought all to have run dorsallj^ of the basi- 

 pterygoid process as in Diplocerckles and the Rhipidistids. 



The basipterygoid process in Wirnania and Macropoma, though 

 situated very high up, issues, however, just at the basis of the 

 obvious homologue of the alisphenold wulst and just below the 

 level of the floor of the cranial cavity. It actually has the same 

 position as in Diplocercides and Axelia, but the cranial basis 

 below it has grown much deeper in these. There is thus no 

 reason to believe that in IVimania and Mao-opoma the trigeminus 

 branches, the lateralis branches accompanying these, and the 

 V. jugularis would have run in another way in relation to the 

 basipterygoid process than in Alexia, Diplocercides, and the 

 Rhipidistids. 



Consequently the view put forward by AUis in a recent paper 

 (1922, pp. 149-152) that the vena jugulai'is, the trigeminus 

 branches, and the lateralis nerves accompanying these passed 

 ventrally of the process termed the basipterygoid process by me 

 seems untenable, as far as we can judge at preseiat- tt is 

 absolutely certain that the basipterygoid process of my descriptions 

 of the Ccelacanthids cannot be a postorbital process as Allis 

 concludes. A single glance at the conditions in Dip>locercides and 

 Axelia is sufficient to show the impossibility of this view. 



In his ai'gument against my view of the basipterygoid process 

 in the Ccelacanthids, Allis also says that as the hyoman- 

 dibula in these fishes is evidently of the teleostome type, the 

 jugular vein must have passed internal to it (Allis, 1922, p. 151 ; 

 1915), and that this vein accordingly cannot have run so high up 

 as I have maintained, i. e. it cannot have run dorsally of the 

 basipterj^goid process. He evidently bases his account {cf. Allis, 

 1922. pp. 150, 151) in this point on Reis's description, having 

 probably oveidooked my statements (Stensio, 1921, pp. 114, 118- 

 119) that the dorsal part corresponding to the hyomandibula of 

 the hyoid ai'ch in the Ccelacanthids is reduced, and that the 

 hyomandibula of Reis's description is simply a parr, of some of 

 the ossifications in the primordial neurocranium. The epihyal, 

 which in the fossil state of the Ccelacanthids forms the dorsal 

 part of the hyoid ai^ch, has been attached to the primordial 

 neurocranium only with ligaments. How far dorsally these 

 ligaments extended it is impossible to say, but it seems to me 

 most probable that they were ratlier short, and that the vena 

 jugularis passed totally dorsally of them and thus dorsally of the 

 hyoid arch, as it does in Selachians. Thus in this respect, 

 too, the conditions do not suppoi't the view put forward by 

 Allis. 



