410 J. BARRELL INFLUENCE OF CLIMATES ON VERTEBRATES 



The Devonian is overlain by the Lower Carboniferous, represented in 

 Nova Scotia and New Brunswick by the Horton Bluff series. 



"This consists of hard sandstones and shales often calcareous, associated 

 with conglomerate and grit, and in some places with highly bituminous shales. 

 They contain underclays and thin coaly seams, remains of Plants, Fishes, and 

 Entomostracans, and footprints of Batrachians, but no strictly marine re- 

 mains." 19 



"No bones of Batrachians have as yet been found in these beds, but the foot- 

 prints indicate the presence at the beginning of the Carboniferous Period, and 

 before the deposition of the Lower Carboniferous limestones, of both large and 

 small species similar to those of the coal formation." 20 



Sir William Logan discovered the first of these footprints in 1841, on 

 a slab of dark-colored sandstone, glazed with fine clay on the surface. 

 The two rows of footprints are about three inches apart, the distance be- 

 tween the impressions in a single row being three or four inches and the 

 individual impressions about one inch in length. 21 



G. F. Matthew, in his classification of batrachian footprints, remarks 

 that the toes are pointed, five on the hind foot and probably four on the 

 fore foot. 22 



In Hylopus hardingi, discovered in the Carboniferous shales of Parrs- 

 boro, the great length of the stride, which is nearly five times the length 

 of the foot and twice as much as the distance between the rows of tracks, 

 apparently indicates that the animal stood as high on its legs as an ordi- 

 nary mammal. 23 



Tracks of a larger type, called by Dawson Sauropus antiquior, were 

 found at Parrsboro in a horizon which Dawson states is probably that of 

 the Horton series. The footprint is about three and one-half inches 

 wide and scarcely half as much in apparent length. It shows four sub- 

 equal toes and an outer toe diverging from the others and showing indi- 

 cations of a short claw. The shortness of the impressions in this species 

 gives them a digitigrade aspect. 24 



A further record of the existence of the Amphibia is found in the 

 Mauch Chunk shales of Pennsylvania. This formation of red shales and 

 sandstones, reaching a maximum thickness of as much as 3,000 feet, 

 occupies the upper half of the Lower Carbiniferous, or Mississippian 

 period. The first impression to be found was that of Sauropus primcevus, 



19 J. W. Dawson : Report on the fossil plants of the Lower Carboniferous and Mill- 

 stone Grit formations of Canada. Geol. Survey of Canada, 1873, p. 5. 



20 J. W. Dawson : Trans. Roy. Soc. of London, vol. 173, 1882, p. 651. 



21 J. W. Dawson : Acadian geology, 3d ed., 1878, pp. 353-355. 



22 Trans. Roy. Soc. Canada, vol. ix, 1903, sec. iv, pp! 109-121. 



23 J. W. Dawson : Trans. Roy. Soc. of London, 1882, p. 653. 

 2 * J, W. Dawson : Ibid., p. 652. 



