NOTACANTHIFORMES 419 



Family FIERASFERIDAE. The dorsal fin is elongated like the anal. 

 Only the premaxillae border the small inferior mouth. Special muscles 

 are developed for dilating the front end of the air-bladder. Neither 

 pelvic fins, nor spines, nor pyloric caeca, nor suborbitals are present. 

 There are exoccipital paired condyles, not found in other Xotacanthi- 

 formes (Emery [131]). Possibly belonging to the Zoarcidae. 



Fierasfer, Cuv. ; widely distributed (Fig. 420). 



Series 6. 



In these fish the air-bladder loses its open communication with 

 the gut, except in the Stephanoberycidae and some of the lowest 

 Acanthopterygians (p. 426) ; the toothless maxilla is usually com- 

 pletely excluded from the margin of the mouth ; the supraoccipital 

 meets the frontals so as to separate the parietals ; and several 

 anterior dermal rays of the dorsal and of the anal fin, and the 

 front dermal ray of the pelvic fins, as a rule, become converted into 

 jointless spines (p. 424). 



Sub-Order 6. MUGILIFORMES (Percesoces). 



The families included in this sub-order form an assemblage of very 

 doubtful phylogenetic value (Starks [418]). They are not bound 

 together by any very distinctive characteristics, and most of those 

 modifications which do occur such as the development of spines, and 

 the moving forward of the pelvic girdle, which may become joined 

 to the pectoral girdle by ligament are approximations to the Acan- 

 thopterygian type of structure. Again, the constant presence of 

 one spine and five (or not more than five) jointed dermotrichs 

 in the pelvic fins, except in the Ophiocephalidae and aberrant 

 Icosteidae, strongly suggests affinity with the Perciformes. As a 

 rule, scales completely cover the head. The Mugiliformes are not 

 known for certain to occur below the Eocene strata. 



TRIBE 1. 



With two separate dorsal fins, the anterior with spines. Except in 

 the Sphyraenidae, the pelvic bones are attached by ligament to the 

 symphysis of the cleithra, and ribs are borne by strong parapophyses. 



SUB-TRIBE A. Family SPHYRAENIDAE. With free pelvic bones, and 

 sessile anterior ribs. The large mouth is armed with formidable teeth. 

 With cycloid scales. 



Sphyraena, Bl., Sch. ; warm seas ; Eocene, Europe and N. America. 



SUB-TRIBE B. Family ATHERINIDAE. The pelvic bones are connected 

 by ligament to the cleithra. The pectoral fins are inserted high up. 

 With cycloid or ctenoid scales. 



