484 WILLIAM K. GREGORY 



Their fins are less specialized than those of the . . . [Halo- 

 sauridae and Notacanthidae] and their trunk is provided with 

 paired longitudinal series of enlarged scutes [Compare Eurypholis 

 among Scopeloids]. " (Smith Woodward loc. cit.) 



Jordan is sceptical as to the naturalness of this assemblage 

 (1905, p. 484) especially as to the inclusion of the Fierasferidae. 

 Possibly this order might be included in the superofder Mesich- 

 thyes defined below (p. 484), but the retention of the very 

 archaic type of cranium militates somewhat against this associa- 

 tion. On the other hand the closure of the air bladder, absence 

 of the mesocoracoid arch, and frequent appearance of spines in 

 the fins seem to separate the group from the Malacopterygii. 

 It may prove advisable eventually to raise the group to super- 

 ordinal rank, coordinate with the Mesichthyes, Thoracostraci, 

 etc., retaining the divisions Lyopomi and Heteromi as orders. 



Superorder Mesichthyes 1 (Hay) mihi. 



E (Plate XXIX.) 



The groups of families known as Iniomi (Scopeloids) , Haplomi 

 (Pikes, etc.), Salmopercae (Sand-rollers), Synentognathi (Fly- 

 ing-fishes, etc.), are all doubtless descended from various soft- 

 rayed, isospondylous, or perhaps even Holostean stocks which 

 had evolved more or less toward the spiny-finned or physoclistous 

 type of structure. Hence these intermediate groups present 

 numerous combinations of the leading characters which dis- 

 tinguish typical soft-rayed and spiny-finned fishes. For example, 

 in some of them (Synentognathi) we find abdominal ventrals and 

 soft or non-articulated rays (Isospondyl characters) , in combina- 

 tion with a closed air bladder (acanthopterous character), 

 while in others (Percopsidae) , which are referred by Boulenger 

 to the Haplomi, an open air bladder, and an adipose dorsal fin 

 persist in combination with forwardly displaced ventrals and 

 spines in the fins. Hence as the passage from typical soft-finned, 

 physostomous, to spiny-finned and physoclistous fishes is very 

 gradual systematists have experienced difficulty in segregating 



1 ^ecros, middle, t'x^vs, fish, in allusion to the transitional character 

 of the group. 



