GREGORY: FISH SKULLS 



397 



(4) thorn-like processes have been developed on many points on the surface of the 

 skull. 



As Lophius dates back to the Upper Eocene, the time of the supposed origin of the 

 lophiid from the antennariid stock must probably be not later than Basal Eocene or Upper 

 Cretaceous. 



Onchocephalids. — In the most highly specialized members of the group, which are 

 typically benthonic, the body (Fig. 268) is depressed, subcircular and almost lense-shaped, 

 studded all over the dorsal surface with spicules and thorns. The greatly enlarged pectoral 

 girdle is included in the disc and free portions of the pectoral fins protrude at the side, like 

 the flippers of a sea-lion. The pelvic fins lie beneath the body disc and, spreading apart 

 widely, serve as hind limbs. The skull in these round-disced forms protrudes but little 



pr crb/r 



sphot y/ 



Fig. 269. Ogcocfphalus. Side view. 



above the disc. In others, however, such as Ogcocephalus vespertilio, the skull (Fig. 269) 

 projects well above the level of the disc and its fundamental characters agree with those 

 of the Antennarius type, as follows: 



(1) the median interorbital and supra-ethmoid fossa is present and bordered by raised 

 orbital flanges of the frontals, as in Antennarius, but in consequence of the shrinking of 

 the illicium the function of this fossa is less apparent; 



(2) the supraoccipital occupies the same median position on the occipital roof but its 

 dorsal surface has now sunk down into a median groove between the raised epiotics; 



(3) the preorbital fork of the frontals and prefrontal is bridged transversely by the 

 vomer and the mesethmoid is depressed below the illicial fossa; 



(4) the neural arches of the first vertebra are enlarged and appressed against the 

 occiput; 



(5) the relations of the opercular, subopercular, branchiostegals, supracleithrum, 

 cleithrum and pediculate pectorals are fundamentally the same as in Antennarius; 



