174 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



below the latter occur the tracks.- This is the only spot where 

 footmarks are found in this valley beneath the trap ; and it proba- 

 bly, though not necessarily, indicates an earlier existence of the an- 

 imals than in those cases where the tracks lie above the trap. 



Species 4. Brontozoum expansum. (PI. III. Fig. 1.) 



Ornithoidichnites expansus, Mass. Geol. Rep., Plate 38, fig. 23. 



Nos. 44, 69, 207, in Cabinet. 



Divarication of the lateral toes, 50° to 70° ; of the inner and 

 middle toes, 25° ; of the middle and outer toes, 30°, Length of the 

 middle toe, 4.6 inches ; of the inner toe, 3.2 inches ; of the outer 

 toe, 4.9 inches ; of the claw, 1.1 inch ; of the foot, 6 to 7 inches ; 

 of the step, 25 inches. Distance between the tips of the lateral 

 toes, 6 inches ; between the tips of the inner and middle toes, 4.2 

 inches ; between the middle and outer toes, 3.4 inches. Projection 

 of the middle toe beyond the lateral ones, 2.4 inches. Width of 

 the toes, one inch to one and a half. Length of the proximal pha- 

 lanx of the inner toe, 1.3 inch ; of the last two, L2 inch; of the 

 first on the middle toe, 1.4 inch; qf the second, 1.3 inch ; of the 

 last two, 1.3 inch ; of the first on the outer toe, 1.6 inch ; of the 

 second, 1.2 inch ; of the third, 0.9 inch ; of the last two, 1.3 inch. 

 Toes straight ; claws normal ; that is, only slightly deflexed from 

 the axis of the toes. Track shown, of the natural size, on Plate 

 3,fig. 1. 



Remarks. — This species has a more massive foot than the B. 

 Sillimanium ; its divarication is greater, and its middle toe short- 

 er. Yet it is not always easy to distinguish the two species. 

 They occur at the same localities, but the former is much the more 

 common. 



