50 ICHNOGRAPHS OF THE 



demonstrated that the animal was a quadruped; that the double impressions on 

 the right of Plate 32 were its anterior, and b b of Plate 31 its posterior feet, 

 which were connected, without solution of continuity, with the impressions of 

 the metatarsi, c c. From a long range of observations, extending over many 

 years, the resulting conclusions were irresistible that the aggregated impressions 

 were due to a leaping animal, and later discoveries corroborate this belief. 



The discovery of another singular feature, that completes the entire group 

 of impressions due to the animal, has been but recently made ; and that is, the 

 impress of the terminal extremity of the vertebral column, or of the truncated 

 os coccygis (PL 31, fig. d). The impress is so excellent that its character is 

 unmistakable, and it reveals a structural organization of the animal that is, perhaps, 

 without existing analogies. Neither, then, is Plate 31, or 32, separately, complete ; 

 but combined, they; include the aggregate of impressions made by the animal 

 when alighting upon the earth, by leaping. Plate 31 lacks the impress of the 

 anterior feet, and Plate 32 that of the coccyx. It will be interesting to examine 

 these several impressions in detail. 



The anterior feet, Plate 32, are constituted each of five massive radiating 

 toes. The central one is largest, and is divided into four phalanges, the two 

 contiguous ones into three, and the two lateral ones into two, each. The carpus 

 that supports the toes does not leave its impress, consequently the footprint is 

 digitigrade. These anterior footprints do not differ essentially, in general form 

 and arrangement, from the corresponding feet of certain other sandstone reptiles; 

 the number and form of the toes is identical, the principal point of difference 

 consisting in magnitude. 



The posterior feet are upon a dissimilar plan, and agree accurately with the 

 bipedal tridactylous footprints. Like the footprints of birds, the inner toe has 

 two, the middle three, and the outer four, phalanges, and each toe is terminated 

 by a stout nail. So far, then, as the number, form, and arrangement of the 

 toes are concerned, there is no difference, however immaterial, between them and 

 those of birds. But the impress of the tarsus, joined in an unbroken piece 

 with that of the foot, is a feature that never exists in the ornithic foot- 

 prints. It was remarked elsewhere, that when the foot of the bird penetrated 

 deeply into the unconsolidated stratum, the inclined position of the leg sinking 

 with the foot left a projecting line running backward from the foot, corre- 

 sponding in length to the depth which the foot itself sunk. But the impress, 



