Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 4:54 FOSSIL FOOTPKINTS. [Oh. XXn. 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, 491). Such Fig. 491. Footprints of a bird. Turner's Falls, Yalley of the Connecticut. (See Dr. Deane, Mem. of Amer. Acad., vol. iv. 1849.) single lines indicate a biped; and there is gener
Elements of geology, or, The Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments elementsofgeolog00lyel Year: 1868 4:54 FOSSIL FOOTPKINTS. [Oh. XXn. 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, 491). Such Fig. 491. Footprints of a bird. Turner's Falls, Yalley of the Connecticut. (See Dr. Deane, Mem. of Amer. Acad., vol. iv. 1849.) 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 relation between the distance separating two footprints in one series, and the size of the impressions; in other words, an obvious proportion between the length of 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 example, 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 living tridactylous birds. Now, such birds have three phalangeal bones for the inner toe, four for the middle, and five for the outer one (see fig. 491); 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 num- ber ; and we see in each continuous line of tracks the three-jointed and five-jointed toes placed alternately outwards, first on the one side and then on the other. In some specimens, 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 impres- sions of the integument or' skin of the foot; but in one fine specimen found at Turn
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