Page:The American Cyclopædia (1879) Volume VII.djvu/350

342 FOSSIL FOOTPRINTS of this formation, but they have not thrown much light upon the animals producing the tracks. Footprints have since been met with in the sandstones of the same formation in New Jersey, and in their probable equiva- lents, the lower triassic sandstones of Lan- cashire and Cheshire in England, and also at Hildburghausen in Saxony. These Eu- ropean footprints have a rude resemblance to the human hand, and were for some time regarded as the marks of an unknown quad- ruped, to which was given the name of chei- rotherium, a supposed marsupial allied to the kangaroo. The track are of considerable di- mensions, and those of the hind and fore feet differ greatly in size. They have since, how- ever, been referred with greater probability to the labyrinthodon, an animal allied to the crocodiles, to which may be due some of the footprints of the Connecticut valley. But be- sides these five-toed and four-footed animals, were those which made the three-toed biped impressions at first regarded as the tracks of birds, and very abundant in the Connecticut sandstones. Prof. Hitchcock finally recog- nized the fact that some of these animals had huge tails, which had left their impressions, and smaller fore feet or paws, which they sometimes put to the ground ; and he then referred them to a kind of bird-like lizards. More recent studies of the fossil remains of these animals, which have been carefully made by various naturalists, and especially by Cope, have made us acquainted with that curious class of animals, the dinosaurs. These crea- tures constituted numerous genera and spe- cies, some of gigantic size, others comparative- ly small ; some feeding on plants, and others carnivorous ; but all remarkable for present- ing a higher type of reptilian organization than any now existing, and approaching in some re- spects to the birds and in others to the mam- malia. Among the vegetable feeders of this group was hadrosauros, a gigantic animal, 20 ft. or more in height, with huge bird-like legs and feet, a lizard-like tail, a diminutive head, and small fore feet or hands, feeding on plants ; while lalaps was an equally huge carnivorous animal of somewhat similar organization. The animals which made the so-called bird tracks in the sandstones of the Connecticut valley were probably similar to these. If we go backward to the palaeozoic period, we find in its upper por- tion, in the rocks of the coal formation in Penn- sylvania, footprints which probably belong to an air-breathing frog-like animal related to the labyrinthodon of the mesozoic. Footprints, ap- parently of batrachian reptiles, are also found in the carboniferous formation of Nova Scotia. These, so far as we know, are the oldest air- breathers, and the remains of animals of this kind which abound in the rocks of this region have been described and figured by Dawson. In the great series of paleozoic rocks beneath the coal, comprising the Devonian, Silurian, and Cambrian, we have numerous ichnolites, but, so far as we know, belonging, unlike those which we have described, solely to fishes or to invertebrate animals. The sandstones at the base of the coal in Nova Scotia are marked with the tracks of a crustacean allied to the limulus or king crab ; and to an animal of that kind are ascribed those curious markings found in the beds of the Potsdam sandstone at several localities in the St. Lawrence val- ley near Montreal, to which the name of pro- tichnites has been given. These tracks, at first supposed to be the footprints of a large tor- toise-like animal, show the presence of sev- eral pairs of walking feet and of a flexible tail. In the same sandstone beds are singular ladder-like markings, which have been called climacticJinites. Dr. Dawson has in this con- nection studied carefully the habits of the king crab, and has shown that when walking on the sands it produces impressions very like pro- tichnites, and when using its swimming feet, markings like climactichnites were the result. In the Chazy and Clinton divisions of the low- er palaeozoic in New York and in Canada are curious bilobate markings, which were sup- posed to be the impressions of a marine plant, and received the name of rusophycus, but according to Dawson are really casts of bur- rows, connected with footprints consisting of a double series of transverse markings, so that a comparison of them with the trails and burrows of limulus justifies the conclusion that they were produced by trilobites. To these markings he has given the name of rusichnites, and has recognized the existence of similar forms in the carboniferous, which he refers to the trilobites of the genus PTiillipsia found in these beds. The curious markings which have been called cruziana, from the lower Cambrian rocks, were probably produced by crustaceans not dissimilar to those which made rusicJinites. Curious parallel notched grooves in pairs, found in the carboniferous of Nova Scotia, have been described and figured by Dawson under the name of diplichnites, and referred by him, with great probability, to fishes having pectoral or ventral fins armed with spines; while in rocks of the same age and still older, down to the base of the Cambrian, are numer- ous grooved and striated markings, some of which may have been produced by the feet or spinous tails of swimming animals. Other markings are with probability ascribed to lin- gula, which, as Prof. Morse has shown, crawls in a worm-like manner over the surface ; while others still are perhaps produced by the trail- ing of seaweeds drifting with tides or currents. Certain markings of this kind have been re- garded as impressions of the stems of plants, and, occurring in the oldest Cambrian rocks, have received the name of eophyton. Accord- ing to Dawson, however, they are more prob- ably the grooves produced by swimming crus- taceans; and he includes under the name of rdbdicJinites all, those rod-like markings. Va- rious imitative markings are met with in rocks,