160 Fossil Footprints of the Connecticut Valley. 



of those varieties represented by figs. 2 and 3, and Mr. H. has con- 

 sequently arranged the original in the order Tetrapodichnites, a 

 term signifying /o«r-/oo/ec? tracks. 



A critical inspection of the several footprints delineated upon 

 the plate, discovers a general similitude, although the contrast in 

 magnitude is so considerable. The comparison is most intimate 

 in those examples represented by figs. 1 and 3, the toes being 

 pachydactylous, or stout, short and blunt, lying in contact, and 

 diverging but slightly. In fig. 2, these members are compara- 

 tively long and slender, or leptodactylous, much separated, yet 

 fall in nearly parallel lines. In two instances only are the toes 

 surmounted with claws, which appendages are short and pointed. 

 But the disagreement between figs. 1 and 3, and fig. 2, is ob- 

 vious in length of stride, that of fig. 2 being equal to fig. 1, while 

 the foot is not one fourth as large. This disproportion alone 

 separates the animals, by which the respective impressions were 

 made, into distinct species. The small imprints cannot be re- 

 ferred to the young of the larger animals, because, on this hypo- 

 thesis the length of step would be in correspondence with the 

 diminished size of the individual. The route of fig. 2 is nearly 

 in a direct line, while in fig. I it is irregular or tortuous, which 

 explains the advanced position of the fore feet in this instance. In 

 both fig. 2 and fig. 3, the fore feet fall a little within and a Httle in 

 advance of the hind feet, and this is the natural order in several 

 other examples which I have seen, the two impressions being 

 nearly in contact. The identity of the impressions is further main- 

 tained by the equal distribution and arrangement of the toes, each 

 foot having three pointed forward, and a stout thumb standing 

 obliquely inward. The difference in point of size between the 

 hind and fore feet, and the divergence of these organs, are gene- 

 ral peculiarities. In fossil footmarks of birds the central toe al- 

 most invariably points in the direction nearly, of the succeeding 

 impression of the opposite foot, or the axis of the foot is in re- 

 verse order to that of the quadrupedal members. 



The impressions represented by figs. 1 and 3 were unquestion- 

 ably produced by identical animals. They display the same 

 massive toes and other affinities, the distinguishing diff"erence 

 being that of size. In numerous examples of this variety, hold- 

 ing an intermediate grade in respect to proportion, the same broad 

 tarsus and fleshy toes exist ; but as has already been intimated, the 



