134 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



out to be varieties of other species, it would reduce the number 

 to thirty-eight species ; thirtj-six of which are found in New 

 England. 



Hitherto I have spoken of names given to the tracks. But two 

 or three years ago, my friend, James D. Dana, Esq., suggested 

 the desirableness of applying names to the animals that made 

 the tracks. Accordingly, at the meeting of the Association of 

 American Geologists and Naturalists in New Haven, in 1845, I pre- 

 sented a catalogue of all the animals then known through their 

 tracks, which was printed in the abstract of the proceedings of that 

 meeting. But as the names were not accompanied by drawings 

 or descriptions, they would not be allowed as authoritative by the 

 rules adopted among naturalists ; and therefore, in this paper, I 

 have made several alterations, as well as additions, and have given 

 full descriptions, as well as outline sketches. And in regard to 

 the latter I would add, that, for the discrimination of species, they 

 are better than full-shaded drawings of individual specimens, be- 

 cause they present more distinctly the essential characters. My 

 outline drawings, moreover, it should be remarked, are not al- 

 ways derived from a single specimen. For when a particular 

 part on one specimen was defective, I have copied that part from 

 other specimens which exhibited it more fully. So that, in fact, 

 the outline tracks which accompany this paper are, in most cases, 

 restored tracks; and yet, in general, they are copied from single, 

 very perfect specimens. In no case is any part supplied by imag- 

 ination ; and hence, in a few instances, I have been obliged to 

 omit some parts of the track. 



My mode of obtaining these outlines, almost without exception, 

 has been, first to trace them exactly upon plates of mica, laid over 

 the tracks, several pieces when necessary being fastened togeth- 



