PALiGOZOOLOGY. 



83 



tire world of extinct corals and shells, are conn- 

 posed, according to Ehrenberg's beautiful dis- 

 covery, of microscopic Polythalamia, many of 

 which are still to be found in our seas, particu- 

 larly in the middle latitudes of the North Sea 

 and Baltic. The first group of the tertiary 

 formation lying over the chalk, a group which 

 it has become customary to designate by the 

 name of the strata of the Eocene period, would 

 appear by no means rightly to deserve this 

 title — "inasmuch as the morning dawn of 

 the nature that still exists with us extends far 

 more deeply into the history of the earth than 

 was until lately believed'X''™). 



As fishes, the oldest of all vertebrate animals, 

 already show themselves in Silurian transition 

 strata, and then occur without interruption in 

 all subsequent formations up to the strata of 

 the tertiary epoch ; as we have seen the Sau- 

 rians begin with the zechstein or magnesian 

 limestone, so are the first mammiferous ani- 

 mals, the Thylactotherium, Prevostii, and T. 

 Bucklandii, which Valenciennes regards as near- 

 ly allied to the Marsupialia(='"), found in the 

 Stonesfield slate, a lower member of the Jura 

 or Oolitic formation, and- the first bird occurs 

 in the older cretaceous depositsC*"). These, 

 according to our present knowledge, are the 

 inferior limits of fishes, saurians, mammalia, 

 and birds. 



But if, among the members of the inverte- 

 brate series of animals, stone corals and serpu- 

 lites are found making their appearance in the 

 oldest formations simultaneously with highly 

 developed cephalopods and Crustacea, the most 

 different and dissimilar orders being, therefore, 

 associated without distinction, we, on the oth- 

 er hand, discover very determinate laws in 

 connection with the distribution of particular 

 groups of the same orders. Fossil shells of the 

 same kinds, goniatites, trilobites, and nummu- 

 lites, compose entire mountains. Where dif- 

 ferent genera are mingled, it often happens 

 that not only is there a determinate sequence 

 of organisms recognizable, according to the re- 

 lations of superposition in the several systems 

 of strata, but the association of certain genera 

 and species has also been observed in the sub- 

 ordinate strata of the same formations. By 

 his happy discovery of the Law of Estimates 

 (Lobenstellung), Leopold von Buch has been 

 enabled to distribute the vast multitude of am- 

 monites into well-characterized families, and 

 shown how the ceratites belong to the mus- 

 chelkalk, the arietes to the lias, the goniatites 

 to the transition limestone and greywacke("'). ! 

 Belemnites have their inferior limits in the \ 

 Keuper >vhich covers the Jura limestone, their I 

 superior limits in the chalk("2). The waters i 

 of countries far remote from one another were 

 inhabited at the same epochs by testaceous an- 

 imals, which partly at least, as' is now known 

 for certain, are identical with those that occur 

 fossilized in Europe. Leopold von Buch has 

 shown us exogyri and trigonia from the south- 

 ern hemisphere (the volcano Maypo, in Chili), 

 and d'Orbigny ammonites and gryphese from I 

 the Himalaya mountains and the plains of Cutch 

 in India, which are identical in kind with those 

 left behind by the old Jurassic sea of France 

 and Germany. 

 Strata characterized by determinate species 



of fossils, or by determinate rolled masses 

 which they inclose, form a geognostical hori- 

 zon, by means of which the geologist, when at 

 a loss, can always ascertain his place, and pur- 

 suing which, he arrives at safe conclusions as 

 to the identity and relative age of certain for- 

 mations, the periodical recurrence of particular 

 strata, their parallelism, and their total sup- 

 pression or failure. If we will thus embrace 

 the type of the sedimentary formation in its 

 greatest simplicity and most general distribu- 

 tion, we find its members in the following or- 

 der, proceeding from below upwards. 



1st. The so-called Transition rocks, in the 

 two divisions of inferior and superior grey- 

 wacke, or Silurian and Devonian systems, the 

 latter formerly designated the Old Red Sand- 

 stone formation ; 



2d. The inferior Trias('*') — Mountain lime- 

 stone, the Coal measures together with the 

 Red conglomerate (Todtlregendes), and Zech- 

 stein or Magnesian limestone ; 



3d. The superior Trias — Variegated-sand- 

 stone, Muschelkalk and Keuper(='8*); 



4th. Jura limestone (Lias and Oolite) ; 



5th. Massive sandstone, Inferior and Superi- 

 or chalk, as the last of the floetz strata, which 

 begin with the mountain limestone ; 



6th. Tertiary formations, in three divisions, 

 which are indicated by the Coarse limestone, 

 Brown coal or Lignite, and Sub-Apennine 

 gravel. 



In the alluvium or drift follow the gigantic 

 bones of the extinct mammalia — the Masto- 

 dons, Dinotheriums, Missuriums, Megatheri- 

 ums, Owen's Sloth-like Mylodon, 11 feet long, 

 &c. With these primaeval genera are associa- 

 ted the fossilized remains of many animals that 

 still exist — the elephant, rhinoceros, ox, horse, 

 deer, &e. The plain near Bogota, filled with 

 the bones of Mastodons (the Campo de Gigan- 

 tes, in which I had some careful digging per- 

 formed) (2"), lies 8,200 feet above the level of 

 the sea, and the bones of extinct species of true 

 elephants are found still higher in the lofty pla- 

 teaus of Mexico. Like the chain of the Andes, 

 which has certainly been upheaved at very dif- 

 ferent epochs, the advances of the Himalaya, 

 the Sewalik hills (which Captain Cautley and 

 Dr. Falconer have so carefully examined), be- 

 sides the extinct Mastodon, Sivatherium, and 

 gigantic land tortoise, the Colossochelys, IS 

 feet long and 6 feet high, contain remains of 

 genera that still exist — elephants, rhinoceroses, 

 giraffes ; and this, which is very much to be 

 regarded, within a zone which enjoys the same 

 tropical climate at the present day which we 

 may be permitted to conjecture prevailed du- 

 ring the epoch of the Mastodons(2"). 



After having thus compared the series of in- 

 organic formations composing the crust of the 

 earth, with the animal remains which lie buried 

 in them, we have still to write another chapter 

 in the history of the organic life of the globe — 

 that, namely, which refers to vegetables ; and 

 to trace the epochs of vegetation, the iloras 

 varying with the increasing dimensions of the 

 dry land, and the modifications which the at- 

 mosphere underwent. 



The oldest transition strata, as already re- 



