THE SCOUTS OF THE REPTILE HORDE. 165 



with long and powerful spines, or, in a later age, with a 

 fearful array of sharp and conical teeth. The dynasty of 

 the fishes sprang up in that period when the limestones of 

 Buffalo, in New York, and of Columbus, Sandusky, and 

 Kelly's Island, in Ohio, were accumulating as sediments in 

 the bottom of the sea ; when Canada West was the ocean's 

 bed, and the last crop of zoophytes was growing upon it ; 

 when the beautiful island of Mackinac was a submarine 

 plantation, and the embryo fastnesses of Old Fort Mackinac 

 witnessed an onslaught and a massacre more bloody and 

 destructive than that of 1761. The empire of the fishes 

 waxed more powerful during the succeeding epochs, when 

 the "black shales" of the West, and, later, the beautiful 

 sandstones of Waverly and Cleveland, Ohio, were the 

 ocean's bed, and hordes of marine forms roamed over the 

 area of Southern New York, and nearly the whole of Mich- 

 igan, Indiana, and Illinois. The Marshall epoch probably 

 covers the latter part of the period of the Old Red Sand- 

 stone of Scotland, whose ichthyic populations have been so 

 graphically described by the author of the " Asterolepis of 

 Stromness." 



The reign of the fishes was prolonged through the Car- 

 boniferous period ; but the types which wielded the sceptre 

 during the later ages of the empire assumed less question- 

 able forms, and began to approach the external configura- 

 tion of the fishes of our day. They were mostly clothed, 

 however, with bony scales, and the backbone extended into 

 the upper lobe of the tail, which was longer than the lower; 

 or, what is probably a more correct view of this structure, 

 the tail was supplied upon the under side with a supernu- 

 merary fin, the development of which deflected upward the 

 true caudal fin — the tail of the sturgeon and the garpike 

 being as truly "homocercal" as that of the whitefish. It is 

 sad to think of the ancient populousness and prowess of 



