THE FOSSIL FOOTMARKS OF THE UNITED STATES. 209 



the sickle shape of the inner toes especially. One can hardly 

 doubt, on inspecting the specimen sketched on Plate 24, fig. 6, re- 

 duced 12 diameters, that the animal was a biped ; yet the inquiry 

 arises, whether it may not have been a quadruped with feet placed 

 like those of the Proteus, exhibited on Plate 19, fig. 3. This is 

 possible ; but the very nearly exact alternation of the tracks in the 

 two rows seems hardly consistent with such a supposition. If we 

 could discover a small fore-foot with each large one, such an alter- 

 nation would be natural ; but no trace of such tracks can be seen. 

 And, upon the whole, my present conviction is, that we must regard 

 the animal as a biped, Avith short legs and a wide body, walking 

 much like the common goose. Had I discovered this slab earlier, 

 I should probably have separated this species from Harpedacty- 

 lus ; but as the thing now stands, such a change is difficult, and 

 perhaps it is not important. I am glad to be able to give a. sketch 

 of the slab in this paper, although the individual tracks are not 

 laid down with quite so much accuracy as I could have wished. 



Species 3. Harpedactylus rectus. (PI. V. Fig. 5.) 



Divarication of the lateral toes, 32° to 38° ; of the inner and 

 middle toes, 10° to 15° ; of the middle and outer toes, 25° to 30°. 

 Length of the inner toe, 2.5 inches; of the middle toe, 3.75 inches; 

 of the outer toe, 2.5 inches ; of the middle toe beyond the rest, 

 1.5 inch; of the foot, 4 inches at least; of the step, 5.5 inches- 

 Heel nearly 2 inches broad ; length not determined. Distance be- 

 tween the tips of the inner and middle toes, 1.5 to 2 inches ; be- 

 tween the middle and outer toes, 2 to 2.5 inches ; between the 

 lateral toes, 2.25 to 3 inches ; between the rows of tracks made 

 by the right and left foot, 3.5 inches. Axis of the foot turned in- 

 ward a few degrees towards the line of direction. Track shown, 



28 



