DEVONIC FISHES OF THE NEW YORK FORMATIONS 1 7g 



lific in information concerning problems of organic descent. The results 

 have, in the author's opinion, an important bearing on the most fundamental 

 questions concerning "living" matter as contrasted with " dead" matter ; 

 for, as stated by Dr Woodward, "we are much more likely to approach 

 some explanation of life by studying the secular development of whole races 

 than by examining the vital processes of individuals or by comparing the 

 members of a single contemporaneous fauna." 



A number of concrete illustrations are given in the paper referred to 

 for the purpose of rendering more intelligible the general outcome of 

 paleichthyological study. The range of examples naturally covers all 

 periods, but in the case of Paleozoic fishes, it is doubtful if a better selec- 

 tion could be made for emphasizing the larger lessons to be drawn from our 

 local faunas, and others in eastern North America, For instance, Ostraco- 

 phores illustrate the principles governing the development of dermal armor ; 

 Acanthodian sharks offer suggestive hints concerning the manner in which 

 paired fins originated ; Crossopterygians and Dipnoans illustrate the trans- 

 formation of paired limbs into paddles ; and among Chondrosteans, early 

 Paleoniscids enlighten us as to the beginning of effective fins. 



An interesting generalization based upon examples occurring among 

 many groups is that all races which do not progress tend to become repre- 

 sented by eel-shaped species in their latter days. We find this to be true 

 of Acanthodians, which declined toward the close of the Paleozoic, and 

 became extinct in the Permian. Their fins, being essentially skin structures, 

 were incapable of the fixation and stiffening by osseus rods after the fashion 

 elaborated by competing groups ; hence they gradually became worsted in 

 the struggle, and, as they declined, their changed habits superinduced an 

 altered form of body. Devonic species having the graceful fusiform pro- 

 portions characteristic of the fleet swimmers become replaced in the Carbonic 

 by unwieldy, overgrown, round bodied creatures like Gyracanthides (text 

 fig. 17, p. 87), that were evidently mud grovelers in land-locked seas and 

 estuaries ; and the latest Permian representatives are almost eel-shaped. 

 It is probable also that the extinction of Arthrodires at the close of the 



