308 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



Introduction. — It is of the highest importance to Geology, that 

 every mammal found in the fossil state should be defined as regards, 

 1st, its specific distinctness, and, 2ndly, its range of existence geo- 

 graphically and in time, with as much exactitude as the available 

 materials and the state of our knowledge at the time will admit. 

 Every form well ascertained becomes a powerful exponent ; while, 

 ill-determined, it is a fertile source of error. For the pure Geologist, 

 in most of his conclusions where age or climatal conditions are in 

 question, is more or less at the mercy of the Palaeontologist, since he 

 must accept the palseontological evidence as it is laid before him, and 

 square his speculations to fit and dovetail into the various mortises 

 which the data inexorably present to him. There is a subordination 

 in the value of the evidence : the higher the form in the scale of 

 organization, the more weighty is the import of its indications. 



The difficulty with which the Mammalian-palaeontologist has to con- 

 tend in arriving at satisfactory results depends doubtless in many cases 

 on the imperfect nature and scantiness of his materials. But it is 

 deserving of remark, that the fossil genera and species which are in the 

 most unsatisfactory and unsettled state, as to definition and nomen- 

 clature, are not those that are the rarest, but often the reverse. Take 

 Mastodon or Rhinoceiws for example, in which the array and con- 

 fusion of specific names are signally perplexing. The reason of this 

 apparent anomaly would seem to be this, — when the remains are few 

 and seldom met with, the species are usually limited in number, and 

 thus more easily discriminated ; on the other hand, when the remains 

 are very abundant over wide areas, the species are at the same time, 

 as a general rule, numerous : and it is well known among naturalists, 

 that the genera which are the most difficult to disentangle specifically 

 are the most complete and natural, where the species are many, and 

 follow each other with the least amount of difference in serial 

 development ; or, in other words, where they are most closely allied to 

 one another. 



Remains of either of the Proboscidean genera, Dinotherium, Mas- 

 todon, and Elephas, abound in all the Tertiary Formations of Europe, 

 Asia, and America, from the Miocene up to the Post-pliocene; they have 

 been the subject of a vast amount of observation, while it is hardly 

 possible to conceive anything more unsettled and opposed than the 

 generally received opinions respecting the species and their nomen- 

 clature in the standard works which are of the greatest authority on 

 the subject. Cuvier, De Blainville, and Owen are agreed in limiting 

 the Elephants and narrow-toothed Mastodons found fossil in Europe 

 each to a single species ; while other palaeontologists consider that the 

 latter group comprises at least three well-marked specific forms, and 

 the former three or four. This palaeontological uncertainty has 

 naturally been reflected in systematic works on Geology, wherever 

 the faunas of the Tertiary Formation are referred to, in statements 

 sufficiently startling, which are repeated at the present day. Thus 

 the Miocene Mastodon angustidens, of the Faluns of Touraine, of the 

 Molasse of Switzerland, and of the Sub-Pyrenees, as also the Miocene 

 Mastodon longirostris of Eppelsheim, are mentioned by Sir Charles 



