CONNECTICUT RIVER SANDSTONE. 49 



analogies to the other quadrupedal impressions of the sandstone rock. The points 

 of difference consist in the superior magnitude of the animals making them, and 

 in the obvious fact that the impressions indicate animals whose organization was 

 of a superior grade, and whose movements were of a more complicated char- 

 acter. All other quadrupedal impressions of the sandstone rock suggest animals 

 having their analogies in the existing orders of reptiles; but these are of a 

 character so anomalous, as to forbid comparison with the pedal organs of known 

 reptiles, and, consequently, if they be really due to reptilian animals, they indi- 

 cate a new and separate order of this class. If the distinctive organizations 

 of the animals, as indicated by the footprints, exclude them from membership in 

 the class of reptiles, an unavoidable inference assigns them to the mammalian 

 class, in which certain types exist that offer, in their pedal systems, more 

 plausible grounds of comparison. The obscure origin of these remarkable foot- 

 prints, and their intricate combinations, have for a long period rendered investi- 

 gation difficult and inconclusive; and it is but recently that the full complement 

 of impressions due to each individual has been discovered. A brief narrative 

 of the discovery of the separate prints that constitute the completed series of 

 impressions, will enable the reader to comprehend the difficulties that have 

 embarrassed investigation, and also to advance, by progressive steps, to a com- 

 prehension of the suite of impressions that indicate one of the most extraordinary 

 of the sandstone creatures. 



In the year 1842, while observing the process of rock cuttings at Turner's 

 Falls, my attention was frequently arrested by solitary footprints, having five 

 radiating toes, that were so perfectly defined as to exhibit their phalangeal 

 system. Subsequently, the impressions were discovered in pairs, planted in oppo- 

 site directions, as represented at the right of Plate 32. As they were not at 

 first seen in consecutive series, or to be associated with other impressions subse- 

 quently developed, their character was enigmatical. In the course of my obser- 

 vations, the oblong concave impressions represented in the lower half of Plate 

 31, c c, which were supposed to be made by the metatarsi of the animal, were 

 developed, and, being associated with the footprints referred to at the right of 

 Plate 32, it was presumed that the creature moved by a succession of leaps, and, 

 dropping upon the ground, rested upon its haunches and anterior feet. This 

 inference was partly correct; but it subsequently appeared that the impressions 

 c c of Plate 31 were each connected with a footprint, hi; and it was then clearly 



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