GREGORY: FISH SKULLS 



187 



which spreads out below on the palatopterygoid arch. The orbit is of fair size and the 

 same is true of the preopercular and opercular. Apparently this type of skull could be 

 derived from that of such a characin as Distichodus. 



\"ery different indeed in appearance is the skull of Ehctrophorus (Gymnotus) electricus 

 (Figs. 725, 73B). This is wide and depressed, with flattened cranium, no inter-frontal 



deffj 



epiot 



A Eigenmannia macrops B Electrophorus electricus 



Fig. 72. A. Eigenmannia macrops. B. EUctrophorus flectricus. Top views. 



fontanelle, a long narrow interorbital bridge and flattened mesethmoid, the latter expanding 

 distally into two rounded plates above the premaxillae. The mouth is relatively large, 

 bordered chiefly by the premaxillae and provided with thick-set small teeth with recurved 

 tips. The maxillse are reduced to small triangular bony flaps at the corners of the mouth. 

 The large dentary has a strong ascending process. The prefrontals (parethmoids) appear 

 to be absent and the roof of the oral cavity is formed chiefly by the greatly expanded 

 entopterygoids, the palatines and ectopterygoids being absent. The symplectic is unusually 

 large and prominent, the hyomandibular much widened anteroposteriorly, especially at 

 the top. One large and two smaller fenestrse perforate its upper part, above the preoper- 



