Ch. XXIL] 



FOSSIL FOOTIRINTS IN CONNECTICUT. 



347 



Fig. 443. 



on the lower surfaces or planes of the strata. If we follow a single line 

 of marks, we find them uniform in size, and nearly 

 uniform in distance from each other, the toes of two 

 successive footprints, turning alternately right and 

 left (see fig. 443). Such single lines indicate a biped ; 

 and there is generally such a deviation from a straight 

 line, in any three successive prints, as we remark in 

 the tracks left by birds. There is also a striking re- 

 lation between the distance separating two footprints 

 in one series and the size of the impressions ; in other 

 Avords, an obvious proportion between the length oi 

 the stride and the dimension of the creature which 

 walked over the mud. If the marks are small, they 

 may be half an inch asunder ; if gigantic, as, for ex- 

 ample, where the toes are 20 inches long, they are 

 occasionally 4 feet and a half apart. The bipedal 

 impressions are for the most part trifid, and show 

 the same number of joints as exist in the feet of liv- 

 ing tridactylous birds. JSTow such birds have three 

 phalangeal bones for the inner toe, four for the middle, 

 and five for the outer one (see fig. 443) ; but the im- 

 pression of the terminal joint is that of the nail only. 

 The fossil footprints exhibit regularly, where the 

 joints are seen, the same number; and we see in 

 each continuous line of tracks the three-jointed and 

 ner£"Faiis, a Valley "of five-jointed toes placed alternately outwards, first on 



Dr C Deane tlC Men/ S of * ne 0ne S ^ e anC * ^ nen 0n * ne °^ ler ' ^ n SOine speci- 



t<Sql' Aead " vo1, iv " meDS > besides impressions of the three toes in front, 

 the rudiment is seen of the fourth toe behind. It is 

 not often that the matrix has been fine enough -to retain impressions of 

 the integument or skin of the foot ; but in one fine specimen found at 

 Tinner's Falls on the Connecticut, by Dr. Deane, these markings are well 

 preserved, and have been recognized by Prof. Owen as resembling the 

 skin of the ostrich, and not that of reptiles.* Much care is required to 

 ascertain the precise layer of a laminated rock on which an animal has 

 walked, because the impression usually extends downwards through sev- 

 eral laminae ; and if the upper layer originally trodden upon is wanting, 

 the mark of one or more joints, or even in some cases an entire toe, which 

 sank less deep into the soft ground, may disappear, and yet the remainder 

 of the footprint be well defined. 



The size of several of the fossil impressions of the Connecticut red sand- 

 stone so far exceeds that of any living ostrich, that naturalists at first 

 were extremely adverse to the opinion of their having been made by 

 birds, until the bones and almost entire skeleton of the Dinomis and of 



* This specimen was in the late Dr. MantelPs museum, and indicated a bird 

 of a size intermediate between the small and the largest of the Connecticut 

 Bpecies. 



