THE OLDEST AIR-BREATHERS 265 



when they actually possessed five, while in other circumstances 

 all may have left marks ; and that, when wading in deep mud, 

 their footprints were altogether different from those made on 

 hard sand or clay. In some instances the impressions may 

 have been made by animals wading or swimming in water, 

 while in others the rain marks and sun cracks afford evidence 

 that the surface was a subaerial one. They are chiefly inter- 

 esting as indicating the wide diffusion and abundance of the 

 creatures producing them, and that they haunted tidal flats 

 and muddy shores, perhaps emerging from the water that they 

 might bask in the sun, or possibly searching for food among 

 the rejectamenta of the sea, or of lagunes and estuaries. 



THE LABYRINTHODONTS OF THE COAL PERIOD, BAPHETES 

 PLANICEPS AND DENDRERPETON ACADIANUM. 



In the summer of 1851 I had occasion to spend a day 

 at the Albion Mines in the eastern part of Nova Scotia, and 

 on arriving at the railway station in the afternoon, found my- 

 self somewhat too early for the train. By way of improving 

 the time thus left on my hands, I betook myself to the ex- 

 amination of a large pile of rubbish, consisting of shale and 

 ironstone from one of the pits, and in which I had previously 

 found scales and teeth of fishes. In the blocks of hard car- 

 bonaceous shale and earthy coal, of which the pile chiefly 

 consisted, scales, teeth and coprolites often appeared on the 

 weathered ends and surfaces as whitish spots. In looking 

 for these, I observed one of much greater size than usual on 

 the edge of a block, and on splitting it open, found a large 

 flattened skull, about six inches broad, the cranial bones of 

 which remained entire on one side of the mass, while the palate 

 and teeth, in several fragments, came away with the other half. 

 Carefully trimming the larger specimen, and gathering all the 

 smaller fragments, I packed them up as safely as possible, and 



