This conclusion, at any rate, is rendered
highly probable by the recent discovery of "Toothed Birds"
(_Odonturnithes_) in the Cretaceous rocks of North America.
[Illustration: Fig. 183.--Lower jaw of _Amphitherium_
(_Thylacotherium_) _Prevostii_. Stonesfield Slate (Great Oolite.)]
[Illustration: Fig. 184. Oolitic Mammals.--1, Lower jaw and teeth
of _Phascolotherium_, Stonesfield Slate; 2, Lower jaw and teeth
of _Amphitherium_, Stonesfield Slate; 3, Lower jaw and teeth of
_Triconodon_, Purbeck beds; 4, Lower jaw and teeth of _Plagiaulax_,
Purbeck beds. All the figures are of the natural size.]
The _Mammals_ of the Jurassic period are known to us by a number
of small forms which occur in the "Stonesfield Slate" (Great
Oolite) and in the Purbeck beds (Upper Oolite). The remains of
these are almost exclusively separated halves of the lower jaw,
and they indicate the existence during the Oolitic period in
Europe of a number of small "Pouched animals" (_Marsupials_).
In the horizon of the Stonesfield Slate four genera of these
little Quadrupeds have been described--viz., _Amphilestes,
Amphitherium, Phascolotherium_, and _Stereognathus_. In
_Amphitherium_ (fig. 183), the molar teeth are furnished with
small pointed eminences or "cusps;" and the animal was doubtless
insectivorous. By Professor Owen, the highest living authority on
the subject, _Amphitherium_ is believed to be a small Marsupial,
most nearly allied to the living Banded Ant-eater (_Myrmecobius_)
of Australia (fig.
Pages:
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384