1859.] on Recent and Fossil Mammalia, 113 



tics of the cetacean class to find the marine deposits which fell from 

 seas tenanted, as now, with vertebrates of that high grade, contain- 

 ing the fossil evidences of the order in vast abundance. 



The red crag of our eastern counties contains petrified fragments 

 of the skeletons and teeth of various Ceiacea^ in such quantities as to 

 constitute a great part of that source of phosphate of lime for which 

 the red crag is worked for the manufacture of artificial manure. 

 The scanty evidence of Cetacea in cretaceous beds seems to indicate 

 a similar period for their beginning as for the soft-scaled cycloid and 

 ctenoid fishes which have superseded the ganoid orders of mesozoic 

 times. 



We cannot doubt but that had the genera Ichthyosaurus, Pliosaurus, 

 or Plesiosaurus, been represented by species in the same ocean that was 

 tempested by the Balasnodons and Dioplodons of the miocene age, the 

 bones and teeth of those marine reptiles would have testified to their 

 existence as abundantly as they do at a previous epoch in the earth^s 

 history. But no fossil relic of an enaliosaur has been found in tertiary 

 strata, and no living enaliosaur has been detected in the present seas : 

 and they are consequently held by competent naturalists to be extinct. 

 In like manner does such negative evidence weigh with me in proof of 

 the non-existence of marine mammals in the liassic and oolitic times. In 

 the marine deposits of those secondary or mesozoic epochs, the evidence 

 of vertebrates governing the ocean, and preying on inferior marine verte- 

 brates is as abundant as that of air-breathing vertebrates in the tertiary 

 strata ; but in the one the fossils are exclusively of the cold-blooded rep- 

 tilian class, in the other of the warm-blooded mammalian class. The Ena- 

 liosauria, Cetiosauria, and Crocodilia, played the same part and ful- 

 filled similar offices in the seas from which the lias and oolites were preci- 

 pitated, as the Delphinidce and Balcenidce did in the tertiary, and still 

 do in the present seas. The unbiassed conclnsion from both negative and 

 positive evidence in this matter is, that the Cetacea succeeded and 

 superseded the Enaliosauria. To the mind that will not accept such 

 conclusion, the stratified oolitic rocks must cease to be monuments or 

 trustworthy records of the condition of life on the earth at that period. 



So far, however, as any general conclusion can be deduced from 

 the large sum of evidence above referred to, and contrasted, it is 

 against the doctrine of the Uniformitarian. 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. -A nd not only as respects the Ver' 

 tebratOy 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 simul- 

 taneous : 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-cora- 

 prehended law. In regard to animal life, and its assigned work on 



Vol. III. (No. 29.) x 



