AVES. 327 



of the integument covering the cushions on the under side 

 of the foot. Such a structure is very similar to that in the 

 ostrich. The average extent of stride, as shewn by the dis- 

 tance between the impressions, was between three and four 

 feet ; the same limb was therefore carried out each step from 

 six to seven feet forward in the ordinary rate of progression. 



These footprints, although the largest that have been ob- 

 served on the Connecticut sandstones, are the most numerous. 

 The gigantic Brontozoum, as Principal Hitchcock proposes to 

 term the species, " must have been," he writes, " the giant 

 rulers of the valley. Their gregarious character appears from 

 the fact, that at some localities we find parallel rows of tracks 

 a few feet distance from one another." 



The strata of red sandstone, with the above-described im- 

 pressions, occupy an area more than 150 miles in length, and 

 from 5 to 10 miles in breadth. " Having examined this series 

 of rocks in many places I feel satisfied that they were formed 

 in shallow water, and for the most part near the shore ; and 

 that some of the beds were from time to time raised above the 

 level of the water and laid dry, while a newer series, composed 

 of similar sediment, was forming." " The tracks have been 

 found in more than twenty places, scattered through an extent 

 of nearly 80 miles from N. to S., and they are repeated through 

 a succession of beds attaining at some points a thickness of 

 more than 1000 feet, which may have been thousands of years 

 in forming."* 



One of the evidences of birds from the Cambridge green- 

 sand, transmitted to the writer by their discoverer, Mr. Barret, 

 is the lower half of the trifid metatarsal, shewing the outer toe- 

 joint much higher than the other two, and projecting back- 

 wards above the middle joint ; it indicates a bird about the 

 size of a woodcock. 



In the conglomerate and plastic clay at the base of the 



* Lyell, Manual of Elementary Geology, 8vo, 1855, p. 348. 



