88 ROYAL SOCIETY OF CANADA 



There is a third species, which I refer provisionally to this genus. 

 Sir Wm. Dawson's Hylopus ( ?) caudifer. Here the disparity in size 

 between the three-toed foot and the other is greater even than in the 

 species last described, and the former has a lighter or shorter heel than 

 the three-toed foot of the other two species. In this species also we 

 note the infrequency with which the impression of the three-toed foot 

 is found : on a slab showing eight footprints of a, consecutive series, 

 only one is that of the fore or three-toed foot. 



As in the preceding species, one might infer that the animal was 

 a biped. To this view, however, there is an objection, which arises from, 

 the presence of a groove which appears to represent the trailing of the 

 belly or tail along the surface of the sand. Tf this animal were bipedal 

 in its movement, it would not be unreasonable to suppose that this " tail " 

 mark would sway from side to side : on the contrary, it continues strictly 

 medial as far as it is impressed on the sand: a narrower median groove 

 in the same track, however, is not strictly central. 



In regard to the two last species, the evidence appears to indicate 

 that the three-toed foot is the fore foot. 



The generic name is in allusion to the rough and irregular foot- 

 print found in most of the species of this genus ; hence a single footprint 

 (or a pair) is often quite insufficient to determine the species. 



The following species is the type of this genus. 



AspEEiPES AviPES n. sp. PI. I, figs. 2a, h. 



Stride about 3 inches (60 mm.), Straddle unknown. The print 

 of the fore foot when present is placed a little behind the hind foot on 

 the line of the stride. 



Hind foot. Length, about 1 inch (35 mm.) ; width, nearly li 

 inch (35 mm.). Five (5) toes, the fourth and fifth set off from the 

 other two and from each other; the first and second toes small, set off 

 from the third and turned broadly inward, the third also turns inward. 

 Sole 15 mm. long and over 15 mm. wide, rounded at the back where it 

 is heavily impressed, and somewhat lobed on the inside. 

 • Angle of digits, I-V=120° ; 1-11=45°. 



The fore foot is 15 mm. long and 20 mm. wide. Three (3) toes 

 widely spread, the outer directed broadly outward, the two others more 

 directly forward; the first and second digits are obsolete. Sole elongate, 

 15 mm. long and 10 mm. wide. Angle of digits, (I-III or) II-V=65° ; 

 (I-IT or) 11-111=50°. ■ 



The sharpness and narrowness of the point of the toes in each foot 

 seems to indicate that they were furnished with claws. 



