230 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



Genus XVII. HOPLICHNUS. 



Feet hoof-shaped ; producing a track like a horseshoe. Quad- 

 rupedal ; hind and fore feet of nearly equal size. 



Species 1. Hoplichnus quadrupedans. (PI. XVI. Figs. 7, 8.) 



Nos. 181-183, in Cabinet. 



Anterior part of the foot semicircular, or forming a portion of a 

 circle. Impression very much resembling a horseshoe. Diameter, 

 1.5 to 2.2 inches. Middle of the foot extending, when the animal 

 was walking, from one to five inches to the right and left of the 

 line of direction. Track shown, of the natural size, on Plate 16, 

 figs. 7, 8. 



Locality. — Turner's Falls, at the Ferry, on the Gill side of the 

 river ; on coarse micaceous sandstone. 



Remarks. — The sketches on Plate 16, figs. 7 and 8, give the 

 shape of the depression in this track ; but no toes are visible. It is 

 possible that the surface on which they occur was a little below 

 where the animal trod, and that the layer of rock above would have 

 shown the toes. It is possible, also, that a slight movement of the 

 sand, after the imprint was made, might have obliterated the toes ; 

 yet no reason can be given why in that case the impression should 

 have been left so uniformly of a circular form. The specimens, 

 however, do show a slight ridge in some cases, extending backward 

 from the track, as if a gentle current had slighdy moved the sand. 

 But there can be no doubt that this animal is generically different 

 from any other described in this paper ; for the fore and hind feet 

 are nearly of equal size, and more nearly circular than any other 

 species. The sketch, on Plate 22, fig. 3, taken from No. 181 of 

 my cabinet, will satisfy any one acquainted with ichnology, that 



