GREGORY: FISH SKULLS 



161 



munity of origin of the two groups. They may indeed have sprung from not distantly 

 related families of Isospondyli, but photophores have also been developed, presumably 

 independently, in Halosauropsis of the order Heteromi (see Boulenger, 1904, p. 621). 

 There are indeed, as Garstang observes, some noteworthy resemblances in the upper jaws 



Cyclothone microdon 



Fig. 54. Cydoihom microdon. Top view. Specimen cleared and stained by Miss Gloria Hollister for Dr. William Beebe. 



between stomiatoids and Iniomi, but the differences between them, pointed out by Bou- 

 lenger (1904, pp. 570, 611), still seem to outweigh the resemblances and to indicate that 

 the stomiatoids are an older branch derived perhaps from Argentina-\\kG salmonoids, while 

 the Iniomi seem to have sprung from elopine Isospondyli. 



OSTEOGLOSSOIDEA 



The superfamily consisting of the Osteoglossidae and the Pantodontidae at the present 

 time has representatives only in the fresh waters of tropical America, Australia, the East 

 Indies and Africa; but in Lower Eocene times the group apparently had its headquarters 

 in the northern hemisphere, fossil Osteoglossidae being known from the Eocene of Wyoming 

 and England. The skulls of the recent representatives combine archaic characters with 

 certain marked specializations, but on the whole the degree of specialization is far less than 



