PUZZLES IN PALAEONTOLOGY. 221 



shrimps. The fish have not developed beyond the low orders of 

 Elasmobranchs and Ganoids, but their remains are so abundant 

 that the Devonian has been called the age of fish. The buck- 

 lered Ganoids must ever be famous to all lovers of literature as 

 well as of geology, through the eloquent descriptions of the poet- 

 geologist, Hugh Miller. He makes us feel the thrill of passionate 

 interest and wonder with which he beheld the strange, seemingly 

 winged, black form which lay before him in the block of stone he 

 had cleft. And there, in hundreds and thousands, did he after- 

 wards find these strange shapes, their wing-like fins stiflened and 

 distorted, as though they had died in an agony of pain — as if the 

 waters of some boiling sea had surged over them, or so they 

 seemed to the self-taught genius who first beheld them. 



Some of the Devonian fishes are remotely related to the 

 sturgeon of modern seas, also to the fringe-finned Polypteri of 

 Africa, and the alligator-gars of America. But many groups are 

 totally extinct. In the Silurian seas the fish attained their largest 

 size. The giant Dinkhthys and Titaniclithys were between twenty 

 and thirty feet long. Their dentition is like that of the Lepido- 

 siren (belonging to the lung-fishes, or Dipnoi), a group of fishes 

 transitional between the true fishes and the amphibians. 



In the Carboniferous epoch the transition has been completed, 

 and we find animals which have developed true lungs, tliough all 

 breathe with gills during some portion of their existence. These 

 early amphibians all belonged to the extinct order of Labyrintho- 

 donts, frog-like in some ai^atomical characteristics, but in form 

 most nearly resembling newts or salamanders. 



"A monstrous eft was of old the lonl and master of earth : 

 For him did the high sun flame, j-nd his river hillo\vin<; ran ; 

 And he felt himself, in his force, to be Nature's crowning race." 



And we know now that these same monstrous efts had pro- 

 bably a large eye in the centre of their skulls, jjrojecting through 

 the parietal suture and moved by powerful muscles. From our 

 childhood we have, with our mind's eye, beheld these monstrous 

 amphibians and saurians of primaeval ages, and now they loom 

 before our imagination in still more monstrous semblance with 

 three huge eyes ! 



There are no traces of the higher plants in the forests of the 



