2 VERTEBEATA. 



CLASS I. — MAMMALIA. 



The fossil relics of the Mammalia Class consist, for the most part, 

 of single and displaced bones, or groups of hones and teeth, and the 

 durable portions of the dermal integument. It is for this reason that 

 Cuvier long ago remarked, that the determination of the remains of Quad- 

 rupeds is beset with more difficulties than that of other fossils. For 

 while shells are often found unbroken, and the skeletons or scaly cover- 

 ings of Fishes occur more or less entire, the complete skeleton of a fossil 

 Mammal is exceedingly rare. 



The earliest trace of a warm-blooded, air-breathing, viviparous 

 animal, appears in the Upper Triassic — the Mtcrolestes, a very small 

 Insectivore, and probably a Marsupial, having been discovered in a 

 bone-breccia at Diegerloch, Wirtemberg. Evidences of several quad- 

 rupeds have been observed in strata of nearly the same antiquity, such 

 as the tooth of the Dromatherium, from North Carolina ; of the Amphi- 

 therium, Amphilestes, JPhascoJotherium, and StereognatJvus, from the 

 Stonesfield Slates ; and of the Spalacotherium, Triconodon, and Pla- 

 giaidax, from the Lower Purbeck beds. Cetacean remains occur in the 

 Grreensand of New Jersey and England. A lapse of time incalculably vast, 

 represented by the Wealden and Cretaceous Periods, intervened between 

 the terrestrial Mammals just mentioned and the Coryplwdon and Palse,- 

 ocyon — the first examples of Mammalian life in the Tertiary. From the 

 Eocene to the present day, an extensive and varied Mammalian fauna 

 has existed, and left remains in the beds of ancient estuaries, lakes and 

 rivers, in peat bogs, marl pits, and especially caves, which served as lairs 

 for predaceous species, and as charnel-houses to their prey. Under the 

 hand of Cuvier the Eocene specimens became the opening chapter to 

 the great volume of Pakeontological Science. 



Order 1 — Bimana. 



This Order, which justly stands at the head of animated Nature, 

 includes only one genus — Homo, — and but one well determined species 

 — sapiens, or Man. He is the only animal truly bimanous and biped ; 

 and he is the only living Mammal having no vacant space in the dental 

 series of the jaw. In him the vertebrate type, which began during 

 the Paleozoic age in the horizontal Fish, finally becomes erect. 



The Palceontological history of Man, before it passes over to Ar- 

 chaeology, is very brief. His creation must have been extremely modern, 

 for his skeleton, more likely to become imbedded in lacustrine or subma- 

 rine deposits than that of any other terrestrial Vertebrate, is found only, 



