564 POPULAR SCIENCE MONTHLY. 



lampreys gave rise to sharks and chimaBras. The sharks developed 

 into rays in one right line, and into the highest sharks along another; 

 while by a side branch through lost stages the primitive sharks passed 

 into dipnoans or lung-fishes. All these types and others abound in the 

 Devonian age and the early records were lost in the Silurian. From the 

 lung-fishes or the ancestors or descendants by the specialization of the 

 lung and limbs, the land animals, at first amphibians, after these rep- 

 tiles, birds and mammals, arose. 



In the sea, by a line still more direct, through the gradual emphasis 

 of fish-like characters, we find developed the crossopterygians with 

 archaic limbs and after these the ganoids with fish-like limbs but other- 

 wise archaic ; then the soft-rayed and finally the spiny-rayed bony fishes 

 which culminate in specialized and often degraded types, as the anglers, 

 globe-fishes, parrot-fishes and flying gurnards. Side branches are the 

 ostracophores, perhaps from primitive lampreys; arthrognaths from a 

 lost ancestry possibly ; chimseras, from primitive sharks, and rays from 

 sharks less primitive; dipnoan sturgeons, gar-pikes and perhaps carp 

 and cat-fishes; and from each of the ultimate lines of descent radiate 

 infinite branches till the sea and rivers are filled, and almost every body 

 of water has fishes fitted to its environment. 



