210 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



of the natural size, on Plate 5, fig. 5 ; and a row of the tracks, re- 

 duced to one sixth the natural size, is shown on Plate 24, fig. 7. 



Locality. — Turner's Falls, Gill, at the quarry, eighty rods above 

 the cataract. 



Remarks. — The specimen from which this species has been de- 

 scribed was in the possession of Mr. Ptolemy P. Severance, but 

 what is to be its ultimate destination is not yet known. A sketch 

 of it, accurately reduced, is given on Plate 24, fig. 7. The spe- 

 cies is distinguished from all others by the long and delicate toes, 

 in connection with an elliptical heel, whose posterior part is not 

 well marked, but which appears to me to approach nearly to that 

 of Harpedactylus concameratus ; and therefore I have placed this 

 species under that genus, though the specific name rectus, as 

 applied to the toes, seems almost to contradict the generic name. 

 It differs from other species, also, by the toes j)ointing so much 

 inward towards the line of direction, and also in the shortness 

 of the step compared with the length of the foot, wliich is more 

 remarkable than in any species hitherto discovered, the ratio 

 between them being only 1.37. Yet the nine steps shown on 

 Plate 24, fig. 7, although somewhat broken, prove conclusively 

 what is the length both of the foot and the step. I have a 

 suspicion that it was a web-footed animal, but no positive ev- 

 idence. This species was discovered while this paper was pass- 

 ing through the press. 



Affinities of the Group. — The probable biped character of most 

 of the species, and the trifid character of the front part of the foot, 

 are presumptions in favor of their being birds. On the other hand, 

 the curved and slender character of most of the toes, the large or 

 long tarsus, forming the heel, and the articulation of the hind toe, 

 when present, so far back upon the tarsus, assimilate them to 



