114 



THE EXTINCT BATEACHIA, REPTILIA 



familiar to all since tin- publication by Hitchcock and Dearie of the histories of the great 

 foot tracks of the Triassic Hod Sandstone of the Connecticut Valley. Such tracks have 

 been discovered by John Smock in the same formation in New Jersey, and by Dr. Chas. 

 Hitchcock in Pennsylvania. Prof. Hitchcock ascribed the tracks described by him to 

 birds. Prof Agassiz* expresses the belief that they were made by vertebrates combining 

 characters of existing classes, perhaps of Reptiles and Mammals, rather than by birds. 

 Now a, carnivorous Dinosaur probably allied to Laelaps, as proven by a portion of the jaw 

 with teeth, in the Academy's Museum, the Bathygnathus borealis of Leidy, has left its re- 

 mains in the red sandstone of Prince Edward's Island, of the same age, and we safely con- 

 clude that some of the large clawed biped tracks of I [itchcock resemble those of that animal. 

 Dr. Leidy has suspected that this would prove to be the case, as he asksf " was this 

 animal probably not one of the bipeds which made the so-called tracks in the sandstone 

 of the Connecticut Valley"?" This inquiry was after an examination of the form of Laelaps, 

 answered in the affirmative. I have ascribed these tracks to Reptiles allied to Laelaps,J 

 and Huxley believes also that they were made by Dinosauria.§ 



The creatures which strode along the flats of the Triassic estuary have been various in 

 species and genera, as pointed out by Hitchcock. Some were purely biped; some occa- 

 sionally supported themselves on a pair of reduced fore limbs. There are impressions 

 where these creatures have squatted on their haunches. One can well imagine the singu- 

 lar effect which these huge gregarious reptiles would produce standing motionless, or 

 marching or wading slowly along the water's edge, ready for a plunge at passing fishes or 

 swimming reptiles. Hut in the active pursuit of terrestrial prey did such an animal as the 

 Laelaps run like the Ostrich, or leap like the Kangaroo. So far as the triassic tracks go, 

 there is little evidence of leapers, chiefly runners, fell upon an exhausted quarry. Or 

 were they only carrion eaters, tearing and devouring the dead of age and disease % Probably 

 some were such, but the prehensile claws of Laelaps a,re like instruments for holding 

 living prey. 



Laelaps has a long femur ; those great leapers the Kangaroos have a short one; the 

 cursorial birds, however, have a similarly short femur, but they do not leap. So this form 

 is not conclusive. The modern Iguanas have a long femur, and they all progress by their 

 simultaneous motion; they only leap; but man with his long femur runs only. The 

 question, then, does not depend on the form of the femur. 



I have suggested, on a former occasion, that Laelaps took enormous leaps, and struck 

 its prey with its hind limbs. I say, in describing it, " the small size of the fore limbs 



* Contrib. Nat. Hist. U. 8., 1857, Vol. I. f Jour. Ac. Nat, Sciences, 1854, 323. 



X American Naturalist, 1S07, 27. Hays' Medical News and Reporter, 1808. 

 § Proceedings Royal Society, Loudon, 1808. Natural Science Review, 1808. 



