io WATSON & DAY, Notes on some Patceozoic Fishes. 



oval bone not represented in Holoptychius. The post- 

 orbital articulates with this bone and with the frontal, 

 which is almost excluded from the orbital margin by a 

 special small supra-orbital bone and by the jugal. The 

 squamosal is a very large element articulating with the 

 post-orbital and jugal and having its upper margin very- 

 free although for some distance it follows the " supra- 

 temporal." The pre-operculum has a narrow exposure 

 and its posterior edge continues the curve of the upper 

 border of the squamosal. The quadrato-jugal is a quad- 

 rilateral bone of a fair size articulated above with the 

 pre-operculum and the squamosal. The circumorbital 

 bones in addition to the post-orbital and jugal include 

 a small crescent-shaped supra-orbital ossicle, a large 

 lachrymal which articulates both with the jugal and with 

 the supra-orbital ossicle, and a bone which is apparently 

 a pre-frontal articulates with the frontal, nasal, lachrymal 

 and the supra-orbital ossicle, and in front ends in contact 

 with a small bone whose anterior margin is a rounded 

 notch which has apparently formed the posterior border 

 of the external nares. The maxilla is the usual long 

 narrow slip forming most of the oral margin and over- 

 lapping all bones which lie above or behind it. A small 

 bone exactly similar to one which we have already de- 

 scribed in HoloptycJiius fills up the gap between the 

 squamosal and the tabular. It is immediately succeeded 

 by a large pentangular operculum whose lower border 

 overlaps the narrow sub-operculum which itself is suc- 

 ceeded by the first of the lateral gulars. We have been 

 unable to observe any distinct post-temporal, but one 

 may be present. The supra-clavicle is a large flat bone 

 whose lower and posterior end passes behind the top of 

 the very massive clavicle. The infra-clavicle is an even 

 larger bone of indescribable shape. We have nothing to 



