GREGORY: FISH SKULLS 



235 



nasals usually very large; occipital articulation tripartite, large exoccipitals meeting broadly 

 beneath the foramen magnum. The osteology and classification of the recent and fossil 

 berycoids were also carefully revised by Tate Regan in 1911. He removed the families 

 Stephanoberycids and Melamphaidae to a new order Xenoberyces, which "differ from typi- 

 cal Berycomorphi in the toothless palate, the absence of a subocular shelf, and the triangular 

 shape of the single supramaxillary but especially in the absence of an orbitosphenoid." 

 Thus the "order" Xenoberyces differs by definition from the Berycomorphi through the 

 loss of a few typical characters. 



Myripristis of the family Holocentridse, the existing species of which live in shallow 

 water in tropical seas, was represented in the Upper Eocene of Monte Bolca, Italy. Its 

 skull (Fig. Ill) shows several specializations beyond the primitive Cretaceous berycoid 



spho+ 



Myripristis murdjan 



M. argyrosomus 



Fig. 111. Myripristis murdjan. 



type. The mandible is rather massive and its distal end is surmounted by a spiny pro- 

 tuberance which fits into a depression between the opposite premaxillse. The posterior 

 end of the maxilla is deep and enters into the gape of the mouth, being bordered by serra- 

 tions. The opercular bears a small spine, the border of the preopercular is finely serrated. 

 The short skull roof is rounded transversely above and behind the orbits. 



In the squirrel-fish Holocentrus ascensionis the premaxillae (Fig. 112) are protrusile, 

 with long ascending processes, while the maxillse have become levers for swinging them. 



