1889.] EOCENE SILTJROID FISHES. 203 



other, so that the centra appear as one bone closely united to the 

 basioccipital, and at their point of union with the latter bone there 

 is a strong; downwardly directed process. 



The Arius skull most closely resembling this fossil is one in the 

 British Museum, which Dr. Giintlier assures me is almost certainly 

 Arms fjagorides. The correspondence between this and the fossil is 

 so close as to leave no doubt as to their generic identity, and the 

 following comparisons refer to this specimen. 1 have to acknowledge 

 my indebtedness to Dr. Giiuther, who on this, as on many other 

 occasions, has spared no trouble in order to facilitate my examination 

 of the specimens under his charge, thereby enabling me to settle the 

 affinities of this fossil fish in a manner which would not otherwise 

 have been possible. 



The frontals of ^. gagorides (fig. 8, /r.) differ from those of the 

 Barton fossil in having the median cleft extended further backwards, 

 and their hinder ends are proportionately wider. The latter cha- 

 racter is in relation to the form of the sphenotics, which are relatively 

 narrower at their hinder part than is the case in the fossil. 



In ordinary bony fishes the post-tempoml is connected with the 

 skull by two processes, one of which is attached to the pterotic 

 (squamosal) and the other to the epiotic ; but the post-temporal of 

 A. gagorides has in addition to these a third attachment by means 

 of a long bar extending from its under surface to the base of the 

 skull (fig. 9), and in addition to this there is a thin plate of bone, 

 vhich may be a process of the post-temporal, extending under the 

 epiotic to the transverse process of the vertebrae. The two upper 

 processes of the post-temporal are ornamented on their upper 

 surface with tubercles, and between them and the pterotic an opening 

 is left which seems to vary in extent in different specimens. The 

 bone to which the hinder of these processes is attached appears 

 from its connections and relations to the auditory region to be the 

 epiotic ; but it may be the parietal. If the latter be the correct 

 interpretation, then the ossicle behind it may be the epiotic ; and 

 the hinder process of the post-temporal certainly reaches thus far. 

 On the other hand, if the parietal be absent and this bone be the 

 epiotic, then the hinder plate will probably be a supernumerary 

 temporal plate, wedged in between the wide hinder moiety of the 

 supraoccipital and the epiotic. 



The post-temporal bone of Arius gagorides has the same structure 

 and relations as that described in the Barton skull ; but the opening 

 left between its two upper processes is not seen in the fossil. This 

 feature, however, varies even in the recent species, and in the fossil 

 the two processes evidently have joined and obliterated the space. 



The pterotic and parietal elements are larger than in the fossil, the 

 last-named bone reaching to the margin of the bony cephalic shield, 

 while in the fossil it seems probable that tiie epiotic and post-tem- 

 poral bones excluded it from the margin. 



The supraoccipital of A. gagorides is an elongated bone con- 

 stricted in the middle, the portion in front of the constiiction 

 corresponding with the part preserved in the fossil. In the main 



