GREGORY: FISH SKULLS 163 



it is in either the Mormyridae or the Clupeidae. The skulls have been very fully described 

 and figured by Ridewood (1905a). 



The otolith of Osteoglossum bicirrhosum, according to Frost (1925a, p. 159), is pen- 

 tangular in shape, in this respect resembling the Jurassic fossil Otolithus {Leptolepidarum) 

 pentangulatus and that of Argentina sphyraena. The front part of this otolith resembles 

 that of Salmo Irutta. In another member of the Osteoglossidse, Heteroiis niloticus, the 

 otolith is more elopine in character, but with certain differences (p. 159). 



:eog 



Fig. 57. Osteoglossum. 



ang 



ossum 



In Osteoglossum, the three species of which are found respectively in Brazil and Guiana, 



Borneo and Sumatra, and Queensland, the skull is fairly primitive in external appearance. 



The surface bones (Fig. 57) are sculptured, the parietals meet in the mid-line, the nasals 



are well developed, all the opercular elements are present and the occiput retains the 



7 



