State Museum of Natural History. 



29 



has confirmed this view of the origin of the foot-prints in an 

 article published in vol. VII of the " Canadian Naturalist," * page 

 71, giving the results of his observations upon the movement and 

 resulting foot-marks of Limulus polyphemus. 



At a later date, 1869, Prof. 0. C. Marsh described a species of 

 Protichnites — P. Logananus t from the Potsdam sandstone at 

 Keeseville, N. Y. This species is much smaller than those from 

 the Potsdam sandstone of Canada, and there is an entire absence 

 of the median grove which is so characteristic of the Canadian 

 forms described by Prof. Owen. 



In June, 1860, Sir W. E. Logan read a paper before the Natural 

 History Society of Montreal, upon the Track of an Animal lately 

 found in the Potsdam formation. J 



The tracks described in this paper are entirely distinct and 

 very different in their characters from any of those before dis- 

 covered, and are identical, at least in generic characters, with 

 those recently discovered at Port Henry, in Essex County, New 

 York. I can scarcely render a better service, to those who will 

 care to study these impressions in this new locality, than to 

 transcribe the paper of Sir W. E. Logan entire, and which I have 

 appended to this communication ; but without expression of 

 opinion as to their origin. 



Sir W. E. Logan has referred these tracks to a crustacean 

 animal, though they are very distinct in their characters from 

 those described as of crustacean origin by Prof. Owen, and from 

 their peculiar character have been designated as Climactichnites. 

 Since we know of no larger fossil forms in the Potsdam sandstone 

 than Trilobites and a single genus related to Limulus, we are 

 naturally led to refer all tracks or foot-prints to crustacean origin 

 for the want of knowledge of any other fossil organisms in the 

 rock capable of making such impressions. The markings under 

 consideration do not appear to have been made by an animal pro- 

 vided with free movable limbs, or otherwise, with very short 

 limbs, without the acute appendages belonging to Limulus. 



* Article XXVI. On the foot-prints of Limulus, as compared with the Protichnites of 

 the Potsdam sandstone. By J. W. Dawson, LL. D., F. R. S., etc, 



t Article V. Description of a new species of Protichnites from the Potsdam sandstone 

 of New York. By 0. C. Marsh, Prof, of Palaeontology in Yale College (with a plate). 



i Article XXXIX. On the Track of an Animal lately found in the Potsdam formation 

 By Sir W. E. Logan, F. R. S. (Read before the Natural History Society of Montreal 

 June, i860.) 



