204 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



than an inch long, shown by dotted lines on Plate 15, figs. 10 

 and 1 1 . Toes and heel nearly straight and very narrow. Width 

 of the foot at the roots of the toes, 0.3 inch ; of the heel, 0.2 inch. 

 Track, shown, of the natural size, on Plate 10, fig. 4. 



Remarks. — The changes of form in the track of this species on 

 successive layers of rock are instructive, and have already been in 

 part described under the third general character. Plate 15, fig. 10, 

 shows the track on the highest layer of No. 175 (Cabinet) ; fig. 

 11 shows the second track, half an inch lower; fig. 12, the third 

 track, one quarter of an inch lower; and fig. 13, the fourth impres- 

 sion, one third of an inch lower. On the upper layers the rock is 

 broken off, so as not to show the extremities of all the toes ; but 

 lower down they are all exhibited, both from their becoming shorter, 

 and from the manner in which the mud was silted into the impres- 

 sion, so as not to fill perpendicularly, but obliquely. 



The species is dedicated to Professor J. W. Bailey, of West 

 Point, the eminent microscopist. 



Plate 19, fig. 6, shows the tracks, on a specimen from Wethers- 

 field (No. 169, Cabinet), of this and the following species, reduced 

 three times from the natural size. They are in relief; and on the 

 other side of the specimen (which is an inch and a half thick), 

 they are much more numerous, so numerous, indeed, that individual 

 tracks can scarcely be traced out. Yet in all these cases, the tracks 

 point nearly in the same direction ; as is the case with almost all 

 the specimens from that remarkable locality, which leads to the in- 

 ference that the animals were gregarious. 



Locality. — W'ethersfield, at the Cove ; on beautiful red shale. 



Species 2. TRia:N0PU3 Emmonsianus. (PL X. Fig. 5.) 



Sauroidichnites Emmoimi, Mass. Geol. Report, Plate 31, figs. 

 5-7. 



