SUCCESSION OF MAMMALIA 



+07 



The principles, based on rigorous and extensive observa- 

 tion of facts, which have thus been inductively established, 

 and have tended to impress upon the minds of the closest 

 reasoners in Biology a conviction of a continuously operative 

 secondary creational law, are the following : — the law of irre- 

 lative or vegetative repetition : the law of unity of plan or rela- 

 tions to an archetype : the phenomena of parthenogenesis : the 

 progressive departure from general type as exemplified in the 

 series of species from their first introduction to the present time. 



Fig. 142. 



The Table (fig. 142) expresses the sum of the observa- 

 tions at the present date, on the succession, appearance, and 

 geological relations of the several orders of the Mammalian 

 class. 



The earliest evidences are of small species, which, when- 

 ever they have presented grounds for ordinal determination, 

 have proved to belong to the low organized Marsupialia. The 

 doubt, when it has existed, lies between this and the Insecti- 

 vorous order, also low in the class according to cerebral 

 characters. One example only, from Stonesfield oolite, the 

 Stcreognathus, may prove to be a minute Ungulate, as is indi- 

 cated by the note of interrogation under Perissodacf/jla. The 



* Owen, " On the Classification and Geographical Distribution of the 

 Mammalia," 8vo, 1859. 



