INTRODUCTION. 
In the endeavour to complete the Natural History 
of any class of animals, the mind seeks to penetrate the 
mystery of its origin, and by tracing its mutations in 
time past, to comprehend more clearly its actual condition, 
and gain an insight into its probable destiny in time to 
come. 
But the researches by which such knowledge is to be 
attained are far from being complete. In many countries 
the fossil remains of former races of animals have been 
neither found nor sought ; where the quest has commenced, 
it dates but a few years back; and in our own Island, 
the geology and fossils of which have been as thoroughly 
investigated as in any other equal portion of the earth, 
much may yet remain, even as regards the usually 
conspicuous and easily recognizable fossils of the highly 
organised animals which form the subject of the pre- 
sent work, to recompense the toil of the Collector and 
the skill of the Interpreter. Nevertheless, the evidence 
already elicited from that part of the earth which, after 
many changes, now constitutes the British Islands, seems 
to afford a sufficient basis for the following outline of the 
Ancient History of its Mammalian Fauna. 
We discern the earliest trace of warm-blooded, air- 
breathing, viviparous quadrupeds at that remote period 
when the deposition of the Oolitic group of limestones had 
commenced. The massive evidence of the operations 
of the old ocean, from which those rocks were gradually 
