THE FOSSIL FOOTMARKS OF THE UNITED STATES. 249 



Remarks. — These tracks occur in the Hamilton group of the 

 Erie division of the New York system of rocks ; and have been 

 particularly described by me in Vol. XLVII. of the American 

 Journal of Science, p. 314. I introduce this species here, because 

 the tracks resemble in form the first species of this genus, although, 

 if the animals that made them were similar, they must have been 

 widely separated in age. I am unable to trace out any satisfactory 

 affinities between the present species and any existing animals, 

 although some crustaceans have extremities with a bifurcation sim- 

 ilar to these tracks. On Plate 24, fig. 1 , it will be seen that the 

 tracks, or pairs of toes, are arranged somewhat in parallel lines. 



Species 3. Harpagopus dubius. (PI. XVIII. Fig. 3.) 



Toes from one and a quarter to two and a quarter inches long, 

 and half an inch wide, with rounded extremities ; arranged some- 

 what on a line, across which the axis of the toes lies at an angle of 

 about 50^. Impressions made by the toes shallow, yet distinct. 

 Three impressions shown, of the natural size, on Plate 18, fig. 3. 



Remarks. — The tracks of this species have less evidence of 

 being those of an animal than the last, from the silurian rocks of 

 New York. Still there is enough of general resemblance to the 

 H. Hudsonius, especially in the form of the impressions and their 

 arrangement along a line, to make it probable that both had a simi- 

 lar origin. This specimen was found by Dr. Deane, at Turner's 

 Falls, and presented to me. I hope that time will throw more 

 light upon it, as well as upon the other species of the genus. It 

 has seemed to me that they exhibit too many evidences of organic 

 origin to be passed in silence. 



33 



