L90 Mr. Lyell on Fossil Mammalia. 



On showing the fossil tooth to Mr. Owen, he at once af- 

 firmed that it was the grinder of some one of the mixed feed- 

 ers, rather than either a purely carnivorous or herbivorous 

 quadruped. His first comparison led him to suppose that it 

 was one of the molars of the lower jaw of an Opossum, about 

 the size of the Didelphys virginiana of North America, to 

 which it in fact bears so great an affinity that it is only di- 

 stinguishable when we observe with care the more quadran- 

 gular form of the molars of the quadrumanes as contrasted 

 with those of the Opossums, in which the anterior and ex- 

 ternal angle of the grinder is cut off as it were vertically. 



When subsequently Mr. Owen instituted a more minute 

 and extensive comparison, with a view of giving an anatomical 

 description of the tooth above-mentioned, he discovered clearly 

 that it was not a Didelphys, but the molar of a Monkey of the 

 genus Macacus, thus constituting at once the first terrestrial 

 mammifer which had been found in the London clay, and the 

 first quadrumanous animal hitherto discovered in any country 

 in tertiary strata as old as the Eocene period. 



Soon after my visit to Kyson, Mr. Searles Wood, having 

 learnt from me that Mr. Owen had determined the tooth above- 

 mentioned to be mammiferous, visited the spot, and prevailed 

 on Mr. Colchester to search in the sand previously thrown 

 aside from the bed containing the numerous teeth of fish. 

 The result of his examination was the discovery of a lower 

 jaw, referred by Mr. Owen to the genus Macacus, containing 

 one molar tooth and the alveolus of another*. 



Pursuing his researches Mr. Colchester afterwards met with 

 another jaw, which is figured in the subjoined notice (see figs. 

 2 a, 2 b, 2 c, pp. 192, 19.3), which Mr. Charlesworth has since 

 described as the jaw of an Opossum -f, a genus to which it will 

 be seen that Mr. Owen also considers it to be in all probability 

 allied. Lastly, in September, 1839, two grinders referred by 

 Mr. Owen to insectivorous bats were also obtained by Mr. Col- 

 chester from the same pit at Kyson. (See fig. 3. p. 194.) 



* See papers by Messrs. Wood and Owen, Mag. of Nat. Hist., Sept. 1839. 

 f Ibid. p. 450. 



