294 Henry Woodward — Dawn of Life on the Earth. 



__i_._. of an inch up to their largest size, which is about -g-Vo* ^'^^ 

 no longer doubts that they are produced by independent organisms, 

 which, like the Globigerina, live and die at the bottom of the sea, at 

 a depth of two miles beneath the surface. 



There seems then to be good ground for the conclusion that the 

 chalk itself is tlie dried mud of an ancient deep sea, and, like the 

 present ooze of the Atlantic, has been slowly accumulated in the abysses 

 of the ocean. We thus see that the Chalk and the Nummulitic Lime- 

 stone are both largely formed of the dead shells of Foraminifera 

 accumulated in deep and wide oceans, which once and again occu- 

 pied the site of the present old world continent. 



But the Chalk furnishes remains of many organisms besides 

 Foraminifera. Ifc has afforded relics of some of the largest of those 

 remarkable flying lizards, the Fterodactyles, at present met with ; 

 whilst the lower beds have also yielded one of the latest forms of 

 land lizards.^ 



Thus we have already extended our researches back sufficiently 

 far to have met with three extinct orders, — the Fterosauria, the 

 Flesiosnuria, and the Dinosauria, — which are only known to us in 

 a fossil state. 



The succeeding Greensand, Neocomian, Wealden, and Purbeck 

 series yield us many more types of these extinct fossil Eeptilian 

 forms, and exemplify in a remarkable degree the changes in climate, 

 and consequently in geographical distribution, which must have 

 taken place to enable such animals to flourish in this country. 



The rare shells of Pleiiroiomaria,^ as also Brachiopoda, were ex- 

 ceedingly well represented in the Oolitic and Cretaceous rocks. 

 Nor do we find many new orders in the Oolitic series with which 

 we are not already made acquainted in the more modern Cretaceous 

 and Tertiary formations. The most interesting form is that of the 

 Archceopteryx, a bird with a remarkably un-avian development of its 

 caudal vertebrae, and possessing free -wing-digits armed with claws. 

 The head of this bird is wanting, but from the more recent dis- 

 coveries of remains of extinct birds by Prof. 0. C. Marsh, in the 

 Cretaceous beds of Kansas, we may reasonably presume that these 

 earlier birds probably possessed mandibles armed with teeth.^ 



The short-necked and massive FUosaurus, which occurs both in the 

 Portland stone and the Kimmeridge Clay, afi'ords us another type of 

 those ancient and extinct sea-lizards once so numerous in the seas of 

 the Mesozoic epoch ; whilst the remains of the great Cetiosaurus 

 and Megalosaurus testify to the magnitude of the land-reptiles of 

 these Secondary rocks. 



But whilst the Eeptilia during the Mesozoic or Secondary Period 

 increased enormously on the face of the earth, and in the waters, 



1 Aeanthopholis, Huxley. 



2 One living example has been obtained from the West Indies, and was valued by 

 M. Damon at -50^. 400 species are known in a fossil state extending from the Lower 

 Silurian to the Chalk. 



3 Prof. Marsh has discovered two— Ichlht/ornis dispar. Marsh, and Apatornis celer, 

 Marsh, both from Kansas, U.S. 



