82 



PALiEOZOOLOGY. 



are still to be discovered in the extraordinary 

 denominations of certain natural bodies. There 

 was the constant disposition to recognize a liv- 

 ing in every extinct species ; just as, in the 

 16th century, false analogies led naturalists to 

 confound the animals of the Old World vv^ith 

 those of the New Continent. Camper, Soem- 

 mering, and Blumenbach, had the merit, by the 

 scientific application of a better comparative 

 anatomy, of first illustrating the osteological 

 portion of Palaeontology (the Archaeology of or- 

 ganic life), in so far at least as the larger fos- 

 sil vertebrate animals are concerned ; but for 

 the proper geological consideration of the Sci- 

 ence of Petrifactions, for the happy combina- 

 tion of the zoological character with the age 

 and order of deposition of strata, we are in- 

 debted to the great work of George Cuvier and 

 Alexander Brongniart. 



The oldest sedimentary formations, those to 

 wit of the transition series, in the organic re- 

 mains which they include, present a mixture of 

 forms vv^hich assume very diflerent places in 

 the scale of development, gradually attaining to 

 greater and greater perfection. Of vegetables, 

 they contain indeed but a few Fuci, Lycopo- 

 diaceae which perhaps were arborescent, Equi- 

 setaceae, and tropical Ferns ; but of animal re- 

 mains, we find, strangely associated together, 

 Crustacea (trilobites with reticular eyes, and 

 calymene), Brachiopoda (spirifer, orthis), the 

 elegant Spheronites, which are nearly allied 

 to the crinoideae("^) and orthoceratites from 

 among the Cephalopoda, Stone-cora!s, and with 

 these lower organisms, Fishes of singular forms 

 in the upper Silurian strata. The heavily-arm- 

 ed family of Cephalaspidans, fragments from 

 whose genus Pterychthys were long regarded 

 as trilobytes, belong exclusively to the Devo- 

 nian, or old red sandstone formation, and show, 

 as Agassiz says, as peculiar a type in the se- 

 ries of fishes as Ichthyosauri and Plesiosauri 

 do among the reptiles(='°). The Goniatites, 

 belonging to the group of Ammonites, likewise 

 begin to show themselves in the transition 

 limestone and greywacke of the Devonian, and 

 even in the later members of the Silurian sys- 

 tem(2"). 



The dependence of physiological gradation 

 upon the age of the formation, which has hith- 

 erto been but little observed in the position of 

 the invertebrate order of animalsc^''^), is exhib- 

 ited in the most regular manner in connection 

 with the vertebrate series. The oldest of these, 

 as we have just seen, are the fishes ; and then, 

 following the series of formations from the in- 

 ferior to the superior, we come to reptiles and 

 mammalia. The first reptile encountered, a 

 saurian or lizard, and, according to Cuvier, a 

 monitor, which had already attracted the at- 

 tention of Leibnitz(='"), makes its appearance 

 in the copperslate floetz of the Zechstein [low- 

 er new red, or magnesian limestone formation], 

 of Thuringia ; and with this, and of the same 

 age, according to Murchison, the palaeosaurus 

 and the codontosaurus of Bristol. The Sau- 

 rian s go on increasing in numbers in the Mus- 

 chelkalk, in the Keuper, and in the Jura forma- 

 tion, in which they attain their maximumC^*^*). 

 Contemporaneously with this formation lived 

 Plesiosauri, with long swan-like necks, con- 

 taining thirty vertebrae ; the Megalosaurus, a 



crocodilian monster, 45 feet long, and with 

 bones of the feet like those of a heavy mam- 

 miferous land animal ; eight species of large- 

 eyed Ichthyosauri ; the Geosaurus or Soem- 

 mering's Lacerta gigantea ; finally, seven sin- 

 gularly hideous PterodactylesC^'^), or Saurians 

 furnished with membranous wings. In the 

 chalk, the number of crocodilian Saurians falls 

 off, yet the epoch which this deposit charac- 

 terizes is distinguished by the Maestricht croc- 

 odile, as it is called, the Mososaurus of Cony- 

 beare, and the colossal, perhaps herbivorous, 

 Iguanodon. Other animals that belong to the 

 present race of crocodiles Cuvier has met with 

 ascending into the tertiary formations(^''*) ; and 

 Scheuchzer's " Man attesting the deluge (ho- 

 mo diluvii testis)," a great salamander, allied 

 to the axolotl, which I brought with me from 

 the Mexican lakes, belongs to the newest fresh- 

 water formations of Oeningen. 



The relative ages of organisms determined 

 by the position of the rocky strata in which 

 their remains are found, has led to important 

 conclusions as to the relations that can be 

 traced between extinct and still existing fami- 

 lies and species (the latter, the species, in very 

 small numbers). Older and newer observa- 

 tions agree in showing that the floras and fau- 

 nas are by so much the more unlike the pres- 

 ent forms of plants and animals, as the sedi- 

 mentary formations in which their remains lie 

 buried belong to the inferior ; in other words, 

 to the older strata. The numerical relations 

 presented by these grand successive changes 

 in the forms of organic life, first pointed out by 

 Cuvier, have yielded decisive results through 

 the meritorious labours of Deshayes and Lyell, 

 in connection more especially with the various 

 groups of the tertiary formations, which con- 

 tain a considerable mass of carefully-studied 

 forms. Agassiz, who has cognizance of 1700 

 species of fossil fishes, and who estimates the 

 number of living species that have been de- 

 scribed, or that are preserved in museums, at 

 8000, speaks out quite decisively, in his mas- 

 ter-work. He says : " With the single excep- 

 tion of one small fossil fish, peculiar to the clay- 

 geodes of Greenland, I have found no animal of 

 this class in all the transition, floetz, and ter- 

 tiary strata, which is specifically identical with 

 any fish now living;" and he adds the follow- 

 ing important observation : " In the inferior 

 tertiary formations, the coarse limestone and 

 London clay, for example, one-third of the fos- 

 sil fishes even belong to genera that are w^holly 

 extinct ; below the chalk there is not one of 

 the genera of fishes of the present time to be 

 found, and the extraordinary family of the Sau- 

 roids (or fishes with scales covered with en- 

 amel, which in structure almost approach rep- 

 tiles, and ascend from the coal formation, in 

 which the largest species lie embedded, to the 

 chalk, where single individuals are still en- 

 countered), stand related to the two families 

 Lepidosteus and Polypterus, which now inhab- 

 it the rivers of America and the Nile, in the 

 same way as our present elephants and tapirs 

 to the Mastodons and Anaplotheriums of the 

 primeval world"^^"). 



The chalk-beds, however, which still contain 

 two of these sauroid fishes, and gigantic rep- 

 tiles, and which present themselves as an en- 



