154 NATURE STUDIES. 



extinct quadrupeds stand in relation to these existing 

 orders in the light of "intermediate forms" or "links." 

 The recent researches of Professor Marsh amongst 

 the American fossil mammals have been fraught with 

 literally surprising results in this latter direction. 

 Prior, however, to Marsh's discoveries, there were not 

 wanting facts which pointed to the conclusion that 

 the demands of evolution for links between the existing 

 orders of quadrupeds would not be made in vain. 

 Take, for example, the single order of the Whales. 

 No more circumscribed and apparently distinct group 

 of animals exists, yet their relationship to other orders 

 of quadrupeds is no mere matter of conjecture, but 

 one of proof. There is a fossil whale known as 

 Zeuglodon, found in Tertiary deposits, and so named 

 from the peculiar double-nature of the molar teeth. 

 Whales with such teeth are unknown to-day, and 

 when the affinities of Zeuglodon are examined, they 

 are seen to point to a clear connexion with the Seals 

 and Walruses, belonging, as we have seen, to the 

 Oarnivora. It would thus seem as if the natural idea 

 that the Seals and Whales were near relations was 

 founded on fact ; and fossil whales certainly tend to 

 bridge over the gulf betwixt the two groups. But 

 this case, powerfully as it argues in favour of the 

 connected series of animals which evolution requires, 

 is by no means solitary. We have long known, for 

 example, of the Anoplotlierium, an extinct quadruped, 

 which presents in itself a curious mixture of the 

 characters of Pigs and Ruminant animals, i. e. t those 



