THE MOHMTRID^, NOTOPTEEID^, AND HTOBONTID^. 211 



right and left supratemporals, also, nearly touch one another 

 above the crauiuni, which is not the case in the Mormyridse. 

 There is a long, slender epiotie limb to the post-temporal in 

 Hyodon and the Mormyridse (except GymnarcJius) , but this is 

 wanting in Notopterus. 



The nasal is a strong, curved, grooved bone in Notopterus 

 and FetrocepJialus, but in Mormyrops, Mormyrus, and Gymn- 

 archus it is more slender, though still conspicuously grooved, 

 while in Hyodon it is a delicate tubular bone of small size. The 

 circumorbital bones are, on the whole, much reduced in the 

 Mormyridse. In Notopterus the suborbitals are rather strongly 

 developed ; in Hyodon it is the postorbitals which have attained 

 the greater development. The inwardly directed processes of 

 the suborbital bones of Notopterus for articulation with the 

 prefrontal and the ectopterygoid respectively are not represented 

 in Hyodon and the Mormyridse. 



The surmaxilla is wanting in all. The gape is premaxilla- 

 maxillary in Notopterus and Hyodon^ the maxilla being well 

 toothed up to near its posterior extremity, but in the Mor- 

 myridse the gape is small and bounded above by the premaxillse 

 only, and the maxillse are edentulous. The right and left pre- 

 maxillse are fused in the Mormyridse (the fusion is not complete 

 in Gymnarchus), which is not the case in Notopterus and 

 Hyodon. The angular bone is distinct and of large size in 

 Notopterus ; in Hyodon and the Mormyridse there is no separate 

 angular. 



The hyomandibular articulates with the cranium by a single 

 broad head in Notopteoms, and by two distinct heads in 

 Hyodon ; in the Mormyridse the whole of the upper edge of the 

 hvopalatiue arch is in close relation with the cranium, and the 

 cranial head of the hyomandibular projects very slightly, if at 

 all, above the upper edge of the metapterygoid. A separate 

 symplectic bone and a separate entopterygoid are recognizable 

 in Notopterus and Hyodon, but not in the Mormyridse. The , 

 palatine is fused with the ectopterygoid in Notopterus, but not 

 in Hyodon, nor in the IVlormyridse. The palatine is fused with 

 the side of the vomer in the Mormyridse, but it is movably 

 articulated, by a single head, in Notopterus and Hyodon. 



In Hyodon the relations of the subopercular are normal, but 

 the bone is rather small in size ; in the Mormyridse the sub- 



15* 



