112 FOSSIL MAMMALIA OF THE 



An easy show of a superior philosophy may be made by a profession of cautious 

 expectancy, an assumption of due power of restraint, of reticence of reasoning, of self- 

 denying abstinence from inference. Bulky Mammals, we may be reminded, are less 

 numerous than dwarf kinds, so the chances of discovery of their remains are fewer ; 

 gyrencephalous Ungulates and Carnivores may still be found at Stonesfield, or Durdlestone, 

 or elsewhere. And, if not, " In what circumstances is the Phascolotherinm more embry- 

 onic, or of a more generalised type, than the modern Opossum? " asks Prof. Huxley, in 

 his character of Advocate for the Uniformitarian view.^ 



There is not, to be sure, much of the old Marsupial left to enable the competent 

 and equal observer to answer this question ; but, if a clear reply be given by but half 

 its jaw, we may infer that the whole animal would have been consistent in its ampler 

 testimony. 



Place the mandibular ramus and teeth of a Bidelpliys by the side of that of 

 Phascolotherimn (as in the specimen in the British Museum), and the more generalised 

 type is conspicuous in the absence of the differentiation of the seven molars in the Oolitic 

 fossil, which differentiation characterises the homologous teeth in the modern Opossum. The 

 canine of the Phascolothere shows but a slight superiority of size over the antecedent teeth, 

 which are of like shape to it, and are divided from each other by similar intervals. In 

 the modern Opossum the canine is marked by greater relative size and diflference of shape 

 from the close-set group of small incisors anterior thereto. The seven molars of 

 Phascolotherium show gradational differences of size, while that of shape is limited to 

 slight simplification of the two smallest, which are the first and last of the seven teeth. 

 In Bidelphys the last four molars are abruptly and markedly differentiated both by size 

 and complexity of structure, from the three preceding ones ; so that zoologists distinguish 

 the four as "true molars^' from the three which are their " false molars." Phascolo- 

 therium shows no such grounds of distinction. 



Only a physical defect of vision could fail to discern these " circumstances " by which 

 the Oolitic Marsupial exemplifies the " more generalised type.^' 



When hazarded assumptions and vague suppositions become facts, right reason 

 will draw the proper deductions. ' In the meanwhile, on the basis gained by the results 

 of the present research, the mind ponders on the prospect commanded over the Mesozoic 

 earth. 



We see, at every level and distance within such range, nothing moving of Mammalian 

 life, save the low and the small ; rat-like, shrew-like, forms of the most stupid and 

 unintelligent order of sucklers. The results of Neozoic palaeontology sometimes move 

 one to exclaim, in regard to Mammals, " there were giants in those days !" but, descend- 

 ing to earlier periods, we find only dwarfs. 



Amongst these initial forms of Marsupialia we may see in Amphitherium the prototype 



' Speaking for Mr. Leonhard Horner, P.G.S., 'Quarterly Journal of the Geological Society of London,' 

 vol. xviii (1862), pi. li. 



