Recent Geological Discoveriet. 198 



Data are wanting to supply the full answer to such a question ; 

 and we are too apt to forgetthat the geological history is rather that 

 of the existing continents and their shores than of the whole 

 earth. Still the facts that v;e possess strongly indicate that lower 

 and more general types of life once abundant, widely extended, 

 and fitted for varied and high places in the scheme of nature, 

 have shrunk within narrow limits in space, number of species, 

 and range of adaptation, as higher or more specialized types were 

 introduced. The Brachiopod shell-fish and Ganoid fishes of the 

 Palaeozoic rocks, and the Cephalopoda and reptiles of the Mesozoic 

 period, are cases in point ; and in like manner, the mammalian 

 types now prevalent in Australia, may once have been general, 

 just as the few ganoids of our modern rivers are little more 

 than memorials of a perished race. Nor need we be sur- 

 prised if the Marsupial mammals should hereafter be found to 

 have presented in the Secondary period grander or more varied 

 forms than the modern or Pliocene Kangaroos and their associates ; 

 and under the same law, we may place the reported discovery, if 

 authenticated, of a tertiary ape more nearly allied to man than 

 any of its modern congeners. 



We have not advanced sufficiently far to see the whole of truth 

 in this matter ; and the relative importance of space and time, and 

 the true value of types of structure in living beings, require to be 

 carefully weighed ; yet these discoveries serve at least to inspire 

 the hope that we shall some day attain to grand and solid general 

 conclusions on the plan of the succession of living beings as 

 gradually developed in the history of the world. 



A curious circumstance connected with the discovery of mam- 

 mals in Secondary rocks, is that nearly all the remains found have 

 been lower jaws and teeth. The number of lower jaws exhumed 

 has been between forty and fifty. With these have been found 

 five upper jaws and one portion of a skull, snd detached bones 

 perhaps sufficient to complete four or five skeletons. To what 

 circumstance does the lower jaw owe its special exemption from 

 destruction? or, is the Avhole simply one of those accidents that 

 show us how little completeness there can be in our knowledge of 

 fossils ? Sir Charles remarks on this point : — 



" As the average number of pieces in each mammalian skeleton 

 is about 250, there must be many thousands of missing bones ; and 

 when we endeavour to account for their absence, we are almost 

 tempted to indulge in speculations like those once suggested to 



