so 



CHAPTER XV 

 BERYCOIDEI 



HE Berycoid Fishes. We may place in a separate 

 order a group of fishes, mostly spiny-rayed, which 

 appeared earlier in geological time than any other 

 of the spinous forms, and which in several ways represent the 

 transition from the isospondylous fishes to those of the type of 



the mackerel and perch. In 

 the berycoid fishes the ventral 

 fins are always thoracic, the 

 number of rays almost always 

 greater than I, 5, and in all 

 cases an orbitosphenoid bone 

 is developed in connection 

 with the septum between the 

 orbits above. This bone is 



FIG. 198. Skull of a Berycoid fish, Beryx 



splendens Cuv. & Val., showing the or- found in the Isospondyli ancL 



bitosphenoid (OS), characteristic of all , .. . c < 



Berycoid fishes. other primitive fishes, but ac- 



cording to the investigations 



of Mr. E. C. Starks it is wanting in all percoid and scombroid 

 forms, as well as in the Haplomi and in all the higher fishes. 

 This trait may therefore, among thoracic fishes, be held to define 

 the section or suborder of Berycoidei. 



These fishes, most primitive of the thoracic types, were more 

 abundant ' in Cretaceous and Eocene times than now. The 

 possession of an increased number of soft rays in the ventral 

 fins is archaic, although in one family, the Monocentrida, the 

 number is reduced to three. Most of the living Berycoidei 

 retain through life the archaic duct to the air-bladder char- 

 acteristic of most abdominal or soft-rayed fishes. In some 

 however, the duct is lost. For the first time in the fish series 

 the number of twenty-four vertebrae appears. In most spiny- 



250 



