PALEONTOLOGY. 273 



curate comparative anatomy, to throw light on the osteolog- 

 ical branch of palaeontology the archaeology of organic life ; 

 but the actual geognostic views of the doctrine of fossil re 

 mains, the felicitous combination of the zoological character 

 with the order of succession, and the relative ages of strata, are 

 due to the labors of George Cuvier and Alexander Brongniart. 



The ancient sedimentary formations and those of transi- 

 tion rocks exhibit, in the organic remains contained within 

 them, a mixture of structures very variously situated on the 

 scale of progressively-developed organisms. These strata con 

 tain but few plants, as, for instance, some species of Fuci, 

 Lycopodiaceae which were probably arborescent, Equisetaceae, 

 and tropical ferns ; they present, however, a singular associa- 

 tion of animal forms, consisting of Crustacea (trilobites with 

 reticulated eyes, and Calymene), Brachiopoda (Spirifer, Or- 

 this), elegant Sphaeronites, nearly allied to the Crinoidea,* Or- 

 thoceratites, of the family of the Cephalopoda, corals, and, 

 blended with these low organisms, fishes of the most singular 

 ibrms, imbedded in the upper silurian formations. The fam- 

 ily of the Cephalaspides, whose fragments of the species 

 Pterichtys were long held to be trilobites, belongs exclusively 

 to the devonian period (the old red), manifesting, according 

 to Agassiz, as peculiar a type among fishes as do the Ichthy- 

 osauri and Plesiosauri among reptiles. t The Goniatites, of 

 the tribe of Ammonites,! are manifested in the transition 

 chalk, in the graywacke of the devonian periods, and even in 

 the latest silurian formations. 



The dependence of physiological gradation upon the age of 

 the formations, which has not hitherto been shown with per 

 feet certainty in the case of invertebrata, is most regularly 

 manifested in vertebrated animals. The most ancient of 

 these, as we have already seen, are fishes ; next in the order 

 of succession of formation, passing from the lower to the up 

 per, come reptiles and mammalia. The first reptile (a Sau- 

 rian, the Monitor of Cuvier), which excited the attention of 

 Leibnitz, || is found in cuperiferous schist of the Zechsteiii of 



* Leop. von Buch, Gebirgsformationcnvon Russland, 1840, 8. 2-1-40. 



t Agassiz, Monographic des Poissons Fossiles du vieux Grit Rouge, 

 p. vi. and 4. 



t Leop. von Buch, in the Abhandl. der Berl. Akad., 1838, s. 149-1G8: 

 Beyrich, UVr. zur Kenntniss des RReinischen Uebergangsgebirges, 1 837. 

 B. 45. 



$ Agassiz, Recherches svr lei Poissons Fossiles, t. i., Inlrod., p. xviii. ; 

 Davy, Consolation in Travel, dial. iii. 



I. A Protisaurus, according to Hermann von Meyer. The rib of 6 

 M 2 



