NO. l8.] TRIASSIC FISHES OF CONNECTICUT. IO, 



rapidly multiplied, became dominant, and replaced the Pro- 

 tospondyli. Living members of the suborder belong to that 

 division of bony fishes known as physostomous Teleostei. 



One of the late Professor Beecher's generalizations, which 

 seems to hold true throughout the animal kingdom, is that 

 spines characterize only the latest representatives of the class. 

 Applying this to the class of Pisces, Dr. Smith Woodward re- 

 marks: "The Acanthopterygii ("spine-finned") are thus the 

 highest and latest fishes of all, though they sometimes eventually 

 descend from their high estate by degeneration. They exhibit 

 all the peculiar changes in the skull, upper jaw, and pelvic fins 

 noticed as first appearing in a variable manner in the Cretaceous 

 Isospondyli. The spiny-finned fishes began by Berycoids and 

 possibly Scombroids in the Chalk, closely resembling, but not 

 identical with genera living at the present day. By the Eocene 

 period, however, nearly all the modern groups of Acanthopterygii 

 had become completely separated and developed, and their sud- 

 den appearance is as mysterious as that of early Eocene 

 mammals." 



The same eminent authority also recapitulates the main out- 

 lines of the evolutionary history of fishes in the following 

 passage : x 



" Fossils prove that the earliest fish-like organisms strength- 

 ened their external armour so long as they remained compara- 

 tively sedentary ; that next the most progressive members of the 

 class began to acquire better powers of locomotion, and con- 

 centrated all their growth-energy on the elaboration of fins; 

 that, after the perfection of these organs, the internal bony 

 skeleton was completed at the sacrifice of the outer plates, be- 

 cause rapid movement necessitated a flexible body and rendered 

 external armour less useful; that, finally, in the highest types 

 the vertebrae and some of the fin-rays were reduced to a fixed and 

 practically invariable number for each family and genus, while 

 there was a remarkable development of spines. As survivors of 

 most of these stages still exist, the changes in the soft parts 

 which accompanied the successive advances in the skeleton can 

 be inferred. Hence palaeontology furnishes a sure basis for a 



1 Woodward, A. S., The Relations of Palaeontology to Biology. Ann. Mag. Nat. 

 Hist., 1906, ser. 7, xviii, p. 314. 



