Prof. Hitchcock on Ichnolithology, or Fossil Footmarks. 305 



are given on figs. 2 and 3, where the rock was split through. 

 We must not judge from these figures that they show the actual 

 width of the animal's toes, for the curvature of the layers of 

 stone extends usually much farther laterally than the width of 

 the toe ; yet the tapering at the end shows that the toes had 

 claws. 



In the American Journal of Science for January, 1844, Vol. 

 xLvi, Dr. Deane has given a description, with drawings, of some 

 very interesting slabs of tracks, which he discovered at Turner's 

 Falls. They were remarkably distinct and very numerous ; and 

 yet it was easy to trace the consecutive tracks, so as to show be- 

 yond question that they were all made by bipeds. Among them 

 the most common was the Ornithoidichnites fulicoides, of which 

 I gave an account two years ago to this Association, when I ex- 

 pressed some slight doubts whether it were made by a biped or a 

 quadruped. This slab shows most unequivocally that it was by 

 the former. So that, up to the present time, we have no certain 

 evidence that more than one species of the tracks in the Connec- 

 ticut valley (viz, the Batrachoidichnites Deweyi,) were made by 

 quadrupeds. 



Among the tracks figured by Dr. Deane, were two varieties re- 

 sembling the O. fulicoides, but smaller; and he leaves it to me 

 to decide whether they are distinct species. The variety of me- 

 dium size he represents as exhibiting a stride almost twice as 

 great as that of the fulicoides ; and I have little doubt, from what 

 I have seen of the tracks of living and extinct animals, that they 

 must be specifically distinct. Bat, as I have no specimen, and 

 the slab has been disposed of to the British Museum, I dare not 

 attempt to describe it from casts. Of the smallest variety I have 

 a specimen, and think it unquestionably distinct. It is a much 

 more slender and delicate species than the fulicoides ; the toes 

 spread less by 20° ; and although both of them are pachydac- 

 tylous, I cannot discover in the small track any evidence of a 

 membranous margin to the claw, which has led me to arrange the 

 former under the pterodactyli. The new species I describe as 

 follows. 



Ornithoidichnites gracillimus. Toes three, all in front, spread- 

 ing 60° : pachydactylous : claws and tuberous swellings distinct ; 

 impression of a double headed extremity of the tarso-metatarsal 



