I 15. 



RETROSPECT. 189 



known in those regions. The fact that the fossil animals 

 hitherto discovered are marsupial, that is, belong to mam- 

 malia which carry their young in a pouch — a type of 

 organization which is the peculiar feature of the existing 

 Australian fauna — is of great interest, for it proves that 

 the present zoological character of the country has prevailed 

 from a very remote period. 



45. Retrospect. — I must now bring to a close this 

 survey of the ancient superficial deposits — those accumula- 

 tions of alluvial debris, which, taken as a whole, are refe- 

 rable to a far more remote period than those which strictly 

 belong to the human epoch ; although the ancient pass by 

 insensible gradations into those of comparatively recent 

 origin. 



In the former discourse I found it necessary to refer 

 to the discoveries of Astronomy, to elucidate the earliest 

 physical conditions of our planet ; in the present I have 

 summoned comparative anatomy to our aid, and have en- 

 deavoured to point out the mode of induction pursued by 

 the palaeontologist, in his inquiries into the fossil remains 

 of animal organization, and by which he is enabled to call 

 forth from their rocky sepulchres, the beings of past ages, 

 and, like the fabled sorcerer, give form and animation to 

 the inhabitants of the tomb. 



From the facts that have been reviewed in the course of 

 this Lecture, the following inferences result. 



First — that the extinction of certain forms of animal 

 organization has extended throughout the period compre- 

 hended in our present researches. We have traced its 

 influence from the partial extirpation of certain existing 

 forms, to the entire annihilation of many species and ge- 

 nera that once were contemporary with man ; as well as to 

 those which lived, and became extinct, antecedent to all 

 traces of the human race. 



Secondly — that while in the modern marine and fluviatile 



