408 



MAMMALIA OF STONESFIELD OOLITE. 



[Oh. XX. 



and Phascolotherium have complicated crowns and two roots (see d, 

 fig. 412), instead of being simple and with single fangs.* 



The only question, therefore, which conld fairly admit of contro- 

 versy was limited to this point, whether the fossil mammalia found 'in 

 the Lower Oolite of Oxfordshire ought to be referred to the marsupial 

 quadrupeds, or to the ordinary placental series. Cuvier had long ago 

 pointed out a peculiarity in the form of the angular process (c, figs. 

 41 V and 418) of the lower jaw, as a character of the genus Didelphys ; 



Fig. 414. 



Tupaia Tana. 

 Eight ramus of lower jaw. 



Natural size. 



A recent insectivorous placental 



mammal, from Sumatra, 



Fig. 415. 



Fiar. 416. 



Fig. 418. 



Part of lower jaw of Tupaia Tana ; 



twice natural size. 



Fig. 415. End view seen from behind, 



showing the very slight inflection of 



the angle at c. 

 Fig. 416. Side view of same. 



Part of lower jaw of Didelphys Asarce ; 

 recent, Brazil. Natural size. 



Fig. 417. End view seen from behind, show- 

 ing the inflection of the angle of the jaw, 

 e,d. 



Fig. 41S. Side view of same. 



and Professor Owen has since confirmed the doctrine of its generality 

 in the entire marsupial series. In all these pouched quadrupeds this 

 process is turned inwards, as at c d, fig. 417, in the Brazilian opossum, 

 whereas in the placental series, as at c, figs. 415 and 416, there is an 

 almost entire absence of such inflection. The Tupaia Tana of Sumatra 

 has been selected by my friend Mr. Waterhouse for this illustration, 

 because the jaws of that small insectivorous quadruped bear a great 

 resemblance to those of the Stonesfield Amphitherium. By clearing 

 away the matrix from the specimen of Amphitherium Prevostii above 

 represented (fig. 412), Professor Owen ascertained that the angular 

 process (c) bent inwards in a slighter degree than in any of the known 

 marsupialia ; in short, the inflection does not exceed that of the mole 

 or hedgehog. This fact made him doubt whether the Amphitherium 

 might not be an insectivorous placental, although it offered some 



* I have given a figure in the Principles of Geology, chapter ix., of another 

 Stonesfield specimen of Amphitherium Prevostii, in which the sockets and roots 

 of the teeth are finely exposed. 



