LIFE IN SECONDARY TIMES 265 



feature of the feet. Again, a tridactyl foot has left tracks so 

 much like those of a Bird that Hitchcock, when he discovered the 

 first of them in Connecticut, called them Ornithichnites, i.e. bird 

 imprints. There were certainly no Birds at the beginning of 

 the Secondary Period. It is therefore impossible to attribute 

 these foot-prints, some of which are four decimetres long, to 

 other than the Theropods, at least provisionally. Pentadactyl 

 four-footed imprints, of which the fore tracks were distinctly 

 smaller than the hind, have also been found. They were made 

 by animals of various sizes, but manifestly of the same species — 

 as if the young had lived with their parents. The steps taken 

 by these larger beasts sometimes equalled a span of two metres. 

 The persistence of these tracks up to the time when new 

 strata were deposited over them, seems to confirm the 

 assumption that these animals were not very numerous, and 

 that the struggle for life was consequently not very active in 

 those regions where their footprints have been discovered. 

 To this unknown animal, which has thus imprinted its foot- 

 steps in the sand, the name of Brontozoum giganteum x has been 

 given. Brontozoum has left in the sand imprints of its tail, as 

 well as of its feet. 



The Theropods had pointed, hooked teeth ; they were 

 carnivorous Reptiles moving in the same manner as Kangaroos. 

 The elevation of the body to an erect position on the hind legs 

 was evidently the result of a habit that had gradually modified 

 the size of the muscles and their points of attachment, 

 modifications which reacted on the bones and on the size of the 

 limbs. This habit is easily explained in the case of carnivora 

 living in thick low bush, and which are obliged to raise their 

 heads above it in order to reconnoitre, watch their prey, and 

 retreat to a place of safety at need. Such a habit had already 

 no doubt begun to be imposed on the Sauropodians, whose 

 hindquarters were better developed than the fore-limbs ; later 

 it was associated with the further habit of leaping. The 

 posterior limbs, still almost plantigrade in Anchisaurus of 

 Connecticut, become gradually digitigrade. Thereafter the 

 smallest toes, which cease to touch the ground, become 

 rudimentary. Zanclodon of the Upper Trias of Wurtemburg, 

 which was three metres in length, and analogous forms in 



1 Brontozoum means " thunder-animal ". We have already met with 

 Brontosaurtis or " thunder-lizard ". 



