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affinities alveolar animal arch articular articulated batrachian beds birds bones bony canine carboniferous caudal cavity centrum chalk characters clay condyle cones convex cretaceous crocodiles crocodilian crown Cuvier dental dentition deposits developed Devonian discovered dorsal eocene evidence existing external extinct feet fishes fore formation fossil ganoid genera genus geological hind Ichthyosaurus impressions inches incisors indicate inner Labyrinthodonts length lias limbs limestone lizards lobe London clay lower jaw mammalian Mammals marginal maxillary miocene modifications molar nostrils Nothosaurus notochord old red oolitic orbits organic ossification outer pair palaeozoic peculiar period Pistosaurus Placodus plates Plesiosaurus pliocene posterior premaxillary premolar present proportions quadrupeds red sandstone remains reptiles resembles ribs ridges rocks saurian shell shew shewn side Silurian siphuncle skeleton skull slender species specimens spines strata structure surface sutures tail teeth tertiary thecodont tion tooth transverse triassic true molars tusks upper jaw valve vertebrae
Seite 442 - But analogy may be a deceitful guide. Nevertheless all living things have much in common, . . . Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form into which life was first breathed."1...
Seite 324 - ... insure them against perishing by numerous casualties to which quadrupeds are exposed during floods ; and if they chance to be drowned, or to die when swimming on the water, it will scarcely ever happen that they will be submerged so as to become preserved in sedimentary deposits.
Seite 434 - To give an imaginary example from changes in progress on an island: — let the organization of a canine animal which preyed chiefly on rabbits, but sometimes on hares, become slightly plastic; let these same changes cause the number of rabbits very slowly to decrease, and the number of hares to increase; the effect of this would be that the fox or dog would be driven to try...
Seite 450 - ... what, I say, have they differed from the artificial instruments which we ourselves plan with foresight and calculation for analogous uses, save in their greater complexity, in their perfection, and in the unity and simplicity of the elements which are modified to constitute these several locomotive organs. Everywhere in organic nature we see the means not only subservient to an end, but that end accomplished by the simplest means.
Seite 448 - Vertebrata, but the sum of the animal species at each successive geological period has been distinct and peculiar to such period. Not that the extinction of such forms or species was sudden or simultaneous : the evidences so interpreted have been but local : over the wider field of life at any given epoch, the change has been gradual; and, as it would- seem, obedient to some general, but as yet, ill-comprehended law. In regard to animal life, and its assigned work on this planet, there has, however,...
Seite 448 - Organic remains, traced from their earliest known graves, are succeeded, one series by another, to the present period, and never re-appear when once lost sight of in the ascending search. As well might we expect a living Ichthyosaur in the Pacific, as a fossil whale in the Lias : the rule governs as strongly in the retrospect as the prospect. And not only as respects the Vertebrata, but the sum of the animal species at each successive geological period has been distinct and peculiar to such period.
Seite 435 - ... of any gradual diminution of the size of such species, but is the result of circumstances, which may be illustrated by the fable of the ' Oak and the Reed ; ' the smaller and feebler animals have bent and accommodated themselves to changes which have destroyed the larger species.
Seite 440 - ... and human objects, was agglutinated to the roof by the infiltration of water holding lime in solution ; that subsequently, and within the human period, such a great amount of change took place in the physical configuration of the district as to have caused the cave to be washed out and emptied of its contents, excepting the floor breccia, and the patches of material cemented to the roof and since coated with additional stalagmite.
Seite 305 - In the gavials, (genus gavialis,) the teeth are nearly equal in size, and similar in form, in both jaws, and the first, as well as the fourth tooth in the lower jaw, passes into a groove in the margin of the upper jaw when the mouth is closed.
Seite 435 - ... the species. If a dry season be gradually prolonged, the large mammal will suffer from the drought sooner than the small one ; if such alteration of climate affect the quantity of vegetable food, the bulky Herbivore will first feel the effects of stinted nourishment ; if new enemies...