398 



TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



(6) the respiratory pore lies behind the enlarged second pterygial in the position that 

 is normal for antennariids. 



We may safely conceive the onchocephalid skull to have been derived from the anten- 

 nariid type by the following modifications: 



Fig. 270. Ogcocephalus. Top and front views. 



(1) the great increase in size of the subopercular and its associated branchiostegal, as it 

 came to form the lateral margin of the disc; 



(2) the reduction of the illicium and the forward displacement of the illicial fossa 

 beneath the newly-formed rostrum; 



(3) in Ogcocephalus vespertilio the "rostrum" appears to represent a great tower of 

 dermal bone, which has grown forward and upward to support excrescences of the skin; 



