482 
SILURIA. 
[Chap. XX. 
covers the Muschelkalk and lies at the base of the Lias). In the ' Bone- 
bed ' of that formation the relics of a small marsupial Mammal were found 
by the late Dr. Plieninger, who named it Microlestes antiquus. Again, the 
late Dr. Ebenezer Emmons, of the United States, described from the lower 
beds of the Chatham Coal-field, North Carolina (of the same age as those 
of Eastern Virginia, and probably of the Wiirtemberg Keuper*), the jaw of 
another minute Mammal, which he called Dromotherium sylvestre. Mr. 
Charles Moore also detected in an agglomerate filling the fissures of the 
Carboniferous Limestone, near Frome, Somersetshire, and composed chiefly 
of the debris of Bhaetic beds (uppermost Triassic), small teeth and bones 
closely resembling those of the Microlestes antiquus of Germany f. 
Lastly, Mr. Boyd Dawkins, of the Geological Survey, has discovered a 
Mammal's tooth in the Bhaetic strata forming reefs exposed at low water 
at Watchet, Somerset J. 
Ascending from the Keuper or summit of the Trias, we have to traverse 
the whole of the Lias and the Lower Oolitic formations (which are charged, 
at intervals, with many terrestrial vegetable remains and highly organized 
Saurians, unlike the Beptiles which preceded them) before we find another 
trace of mammalian life. Insects, which, as has been shown, first appeared 
in the era of the earliest great forests (Devonian, p. 439), became more 
abundant in these Secondary rocks ; and with these are found the bones of 
that oldest known winged Beptile, the Pterodactyle. Still, surrounded as 
we are in these strata by Plants, Insects, and many Beptiles, we have to 
journey through several of the Secondary deposits before we obtain other 
evidences of the existence of Mammalia than a few jaws and fewer ver- 
tebrae of the little Marsupial Phascolotherium Bucklandi (Broderip) of the 
Stonesfield Oolite §, and its (possibly placental) companions Amphilestes, 
Amphitherium, and Stereognathus. 
Passing upwards through the higher Oolitic deposits, and rising con- 
siderably in the scale of formations, — where, in short, we are about to take 
leave of the Oolitic or Jurassic group, and are entering into the mass of the 
great estuarine formation, the Wealden, and approaching the base of the 
Cretaceous rocks, there it is, as might have been anticipated, that geologists 
have discovered proofs of the existence of many more Mammals than have 
been detected in any of the Lower Secondary deposits. Through researches 
which began under the direction of Edward Forbes, and which a few years 
ago unfolded great fossil wealth to the labour and acumen of Mr. Beetles, 
a perfect mine of highly organized small Mammalia was opened out in the 
* I cannot admit that the beds in which the 
small Mammal Dr. Emmons described were en- 
tombed can be referred to the Permian group, or 
close of the Palaeozoic era. The absence of Per- 
mian Mollusks, now known in other parts of North 
America (see p. 470), invalidates his view ; and I 
have yet to learn that Sir C. Lyell or any geolo- 
gist would consider the beds in question to be 
older than the Keuper of Germany. Dr. Em- 
mons's views respecting the supposed Permian age 
of the Chatham coal are also criticised in Professor 
E. Jones's ' Monograph of the Fossil Estheria? ' 
(Palseontographical Society), 1862. 
t See Professor Owen's description of the ver- 
tebras, Quart. Journ. Greol. Soc. vol. xvi. p. 492. 
I Quart. Journ. Geol. Soc. vol. xx. p. 409. 
I It was in the year 1827 that the ' Didelphys 
Bucklandi ' was described by that sound natura- 
list, my friend the late Mr. W. Broderip (Zoologi- 
cal Journal, vol. iii. p. 408). 
