IxXVi PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



mals, as well as in the land and freshwater mollusca, the differences 

 are very slight; amongst the mammifers it is generally the contrary. 

 The analogy of the Quaternary and modern faunas is subject to its 

 own particular law in each natural division ; it is the more striking 

 in proportion as the animals under consideration are of smaller size. 

 If we examine the fossil Mammaha of the southern hemisphere, 

 either by orders, by famihes, or by genera, we first find that the 

 animals are larger than their congeners of the present day; and 

 secondly, that the species which are identical with those of the 

 present day, or nearly so, are the smallest. 



After alluding to the theory of Prof. Owen in his Memoir on the 

 Megatherium, in which he endeavours to explain why the races of 

 smaller forms of animals have had a more prolonged existence than 

 those of greater size, viz., because they could more easily accommodate 

 themselves to those changes in the conditions of life under which the 

 larger forms could no longer exist, he observes that, as a general 

 rule, we find in the different classes of fossil animals the duration 

 of species, and even of genera, is in an inverse ratio to their size and 

 mass, whereas the normal life of individuals is generally in a direct 

 ratio to their size. 



" It is," he observes, in conclusion, ^' a mere question of time, for 

 which man, still new on the surface of the earth, has no chrono- 

 meter to enable him to measure the periods of existence of the beings 

 which surround him. Palaeontology, it is true, reveals to us the 

 existence of gigantic reptiles in past ages, which have successively 

 appeared and disappeared; and the small animals, their cotemporaries, 

 have equally undergone the inevitable law of the renewal of types, 

 both large and small, and of their continual replacement. It is 

 true, we do not observe this movement about us ; we are disposed 

 to believe that organic nature, which, since the beginning of crea- 

 tion, has never ceased to modify itself, has become immoveable since 

 Man's appearance, that the laws of succession have been replaced 

 by mere laws of preservation ; in a word, that creation is complete 

 and finished. 



" This, undoubtedly, is an illusion, caused by this fact, that the 

 few dozen centuries which constitute our history are not sufiicient 

 to bear witness to any important changes ; but if study and observa- 

 tion have taught us anything, it is this, that the history of the whole 

 human race is of no more account in the history of nature than the 

 life of those ephemeral insects of which a single day beholds the' 

 birth, the reproduction, and the death." 



An interesting Monograph has been lately published by Dr. G. A. 

 Maack, entitled ' Palseontological Inquiries respecting hitherto un- 

 known Lophiodon Fossils from Heidenheim on the Hahnenkamme 

 in Central Franconia, together with a Critical Review of all the 

 hitherto known species of the genus Lophiodon.'' In describing the 

 historical development of this genus, the author remarks that the 

 great gap which exists between the Ruminants and Multungula 

 (Vielhufer) of the existing fauna has been in a great measure 

 filled up by the discovery of fossil remains. The contrast hitherto 



