AMERICAN GEOLOGY FOSSIL FOOTPRINTS. 631 



found at the same time were recognized as those of quadrupeds, and 

 wore described under the generic name of Spheropezvum. 



In the Memoirs of the American Academy of Arts and Sciences for 

 1S-19, Deane had again a paper on fossil footprints of the Connecticut 

 Valley, which he regarded as in part those of birds and in part those 

 of reptiles. These were described and figured, but no attempt at 

 classification was made. 



In 1858 Hitchcock published his Ichnology of New England, a 

 quarto volume of some 200 pages, with 60 plates of footprints and a 

 map of the Connecticut Valley, showing the distribution of the Tri- 

 assic sandstone with its included tracks, together with a section across 

 the valley at Springfield. This work is of importance, not merely 

 on account of the detailed description of the tracks, but also as sum- 

 ming up the knowledge of the subject and the prevailing opinion 

 regarding the origin and age of the sandstone itself. The sandstone, 

 it should be stated, had been regarded by many geologists as owing 

 its present dip to its having been deposited upon a sloping floor. 

 To this view Hitchcock now took exception and could find no way of 

 escaping from the opinion that it had been upheaved since its deposi- 

 tion. The age of the sandstone he considered to be undoubtedly 

 Jurassic. He discussed in great detail the character of the tracks, 

 and announced some thirty characteristics which he regarded as based 

 on the principles of comparative anatomy and zoology, and which he 

 thought afforded him reliable grounds from which to judge of the 

 nature of an animal from its tracks. He felt that he could now decide 

 with a good degree of confidence, first, whether the animal making 

 the track was vertebral or invertebral; second, whether a biped, 

 quadruped, or multiped; third, to which of the four great classes of 

 vertebrates it belonged and, with less certainty, to what order, genus, 

 or species the animal might be referred. It was in this work that he 

 first proposed the term Lithichnozoa (the stony-track animals), to 

 embrace the animals whose characters he described from their tracks. 

 The classification adopted divided the animals into ten groups: First, 

 marsupialoid animals; second, pachydactylous, or thick-toed birds; 

 third, leptodactylous, or narrow-toed birds; fourth, ornithoid lizards 

 or batrachians; fifth, lizards; sixth, hatrachians; seventh, chelonians; 

 eighth, fishes; ninth, crustaceans, myriapods, and insects; and tenth, 

 amiclidanx. 



It will be noted that the Brontozoum was still included under the 

 group of pachydactylous or thick-toed birds. 



In 1863 we find Hitchcock again returning to the subject in a brief 

 paper in the American Journal of Science for that year, in which he 

 announced that, though having been compelled to give up ten or a 

 dozen of his old species of footmarks, he had described over thirty 

 new ones. Further, finding that an error had been made as to the 



