60 Mr. Owen on the Phascolotherium. 



We have next to consider those arguments which have been founded on ad- 

 mitted structures. 



The advocate of the mammiferous nature of the Stonesfield Thylacothere allows 

 that it has an unusual number of molar teeth, it may be twelve, true and false, on 

 each half of the lower jaw ; but he denies the inference, that, therefore, this half- 

 jaw has not belonged to a Mammal. There is not sufficient constancy in the num- 

 ber of the teeth in the Mammalia, or even in the carnivorous or insectivorous sub- 

 divisions of that class, to render the excess of teeth in the Thylacothere of any 

 value as an indication of its classial relations. Among the placental Carnivora the 

 Canis Megalotis has constantly one more grinder on each side of the lower jaw than 

 the usual number. Among the Insectivora the Chrysochlore has also eight instead 

 of seven molars in each ramus of the lower jaw. Among the Marsupiata the ge- 

 nus Myrmecobius has nine molars on each side of the lower jaw. Some of the in- 

 sectivorous Armadillos and of the zoophagous Cetacea offer examples of a combina- 

 tion of still more numerous and reptile-like teeth, with all the true and essential 

 characters of the mammiferous class. The anatomist, contending for the saurian 

 nature of the Stonesfield jaws, must have felt the weakness of his cause when he 

 appealed to the number of the teeth in that fossil for its support. 



All the spurious molars of the Thylacotherium have two well-developed fangs : but 

 this fact has also been adduced as an objection to the Cuvierian determination of 

 that extinct animal. The greater number of the spurious molars, however, in 

 every genus of the placental Fera, have two fangs, and in the marsupial Mam- 

 malia, as well as in the Mole, and some other Insectivora, the whole of the false 

 molars invariably possess two fangs, and this structure as little co-exists with a 

 complicated crown of the tooth as in the extinct Thylacothere. 



If the ascending ramus of the Stonesfield jaws had been absent, and with it the 

 evidence of their mammiferous nature afforded by the condyloid, coronoid and an- 

 gular processes, — the structure of the teeth, and especially the implantation of the 

 molars in distinct sockets by means of long double fangs, would, nevertheless, have 

 yielded proof that the fossils in question were the remains of a species referrible to 

 the highest class of animals. Since a Shark's tooth is never implanted in a socket, 

 its form, whether it have a bifurcate base or not, cannot afford any argument for 

 the non-mammalian nature of the Thylacotherium : the saurian nature of the so- 

 called Basilosaurus is too problematical for the attachment of any value to an ob- 

 jection founded on the two-fanged structure of its teeth*. 



When also it is recollected that Cuvier described and figured (after Garriga) 

 the teeth of the Megatherium as having two fangs, and when the origin of that 



* See Bru's Descripcion del Esqueleto de un Quadrupedo muy porpulento y raro, &c. Folio, Madrid, 

 1796. 



