20 Secondary Fossils. 



developed coronoid processes, cannot have belonged to fish 

 or reptiles. I shall merely allude to the late discovery of a 

 more perfect jaw, which enabled Professor Owen''s anatomical 

 skill to decide that the angular process of the Ainphitherium 

 Prevostii was bent inward in a slighter degree than in any of 

 the known marsupialia. The fact of the inflection not ex- 

 ceeding that observable in the jaw of the living mole or the 

 hedgehog, turns the scale in favour of the affinities of the 

 Amphitherium to the placental insectivora, although it still 

 approximates in some points of its osteology to the Myrme- 

 cobius and other marsupials of Australia. 



But the precious relic of another mammiferous genus dis- 

 covered in the slate of Stonesfield, called Didelphys Bucklandi 

 by Broderip, and Phascolotheriwn by Owen, manifests so 

 complete an agreement with the living genus Didelphys in 

 the number of premolar and molar teeth, in the general form 

 of the jaw, and in the extent and position of its inflected 

 angle, that we can hardly doubt its marsupial character, — 

 a conclusion of no small importance, because in this case we 

 have osteological evidence that both the placental and mar- 

 supial classes of mammalia were already in being in an early 

 part of the oolitic era, just as opossums now co-exist with 

 skunks on the American continent. Several insects, and 

 among them the elytra of beetles, on which these small quad- 

 rupeds may have fed, are preserved in the same rock ; and 

 Prof. Owen remarks that some carnivorous quadrupeds of 

 coeval date could scarcely have been wanting to keep down 

 the numbers of the Phascolotheres and Amphitheres, which 

 were probably, like the quadrupeds now most nearly allied 

 to them, quick breeders*. 



By a singular accident, no other bones have been collected 

 of the skeletons of the seven individuals as yet found at 

 Stonesfield, except seven half lower jaws ; a fact demon- 

 strating in a marked manner the fragmentary nature of the 

 memorials handed down to us of an ancient terrestrial fauna. 

 Yet no small diligence has been used by collectors for more 

 than a quarter of a century to obtain even the smallest iso- 

 lated bones of fish and reptiles from these beds. I can only 



* Brit. Foss. Mamm., Introduction, p. 14. 



