180 Mr Whewell's Address to the 



not be eliminated. The exception^ on wliicli this very instructive point 

 was triedj consisted in a few jaw-bones of a fossil animal, which, though 

 occurring in the Stonesfield slate near Oxford, a bed belonging to the 

 oolite formation, had been referred by Cuvier to the genus Didelphys, 

 and thus placed among marsupial mammals. In August last, M. de Blain- 

 ville stated to the Academy of Sciences of Paris his reasons for doubting 

 the justice of the place thus assigned to the fossil animal. Founding his 

 views principally upon the number and natur.e of the teeth of the fossil, 

 he asserted that the animal, if a mammal, must come nearest the phocse ; 

 but he rather inclined to believe it a saurian reptile ; following, as he 

 conceived, the analogies offered by a" supposed fossil saurian described 

 by Dr Harlan of Philadelphia, and termed by him Basilosaurus. M. Va- 

 lenciennes, on the other hand, asserted the propriety of the place assigned 

 by Cuvier to the fossil animal, although he made it a new genus ; and 

 gave to the species the name Thylacotheriian Prevostii. The contro- 

 versy at Paris had its interest augmented when Dr Buckland, in Septem- 

 ber, carried thither the specimens in question. From Paris the contro- 

 versy was transferred hither in November, and principally occupied our 

 attention at our meetings till^the middle of January. 



" One advantage resulting from the ample discussion to which the ques- 

 tion has thus been subjected, has been, that even those of us who were 

 previously ignorant of the marks by which zoologists recognise such dis- 

 tinctions as were in this case in question, have been put fully in posses- 

 sion of the rules and the leading examples which apply to such cases. 

 And hence it will not, I trust, be deemed presumptuous, if, without pre- 

 tending to any power of deciding a question of zoology, I venture to 

 .state the result of these discussions. It appears, then, that some of the 

 marks by which the under jaws of Mammals are distinguished from those 

 of Saurians are the following: (1) a convex condyle; (2) a broad and 

 generally elevated coronoid process ; (3) rising near the condyle j (4) the 

 jaw in one piece ; (6) the teeth multicuspid, and (6) of varied forms, 

 (7) with double fangs ; (8) inserted in distinct sockets, but (9) loose and 

 not anchylosed with the jaw. In all these respects the Saurians differ ; 

 having, for instance, instead of a simple jaw, one composed of six bones 

 with peculiar forms and i-elations, and marked by Cuvier with distinct 

 names ; having the teeth with an expanded and simple fang, or anchy- 

 losed in a groove, and so on. Of course, it will be supposed, by any one 

 acquainted with the usual character of natural groups, that this line of 

 distinction will not be quite sharp and unbroken, but that there will be 

 apparent transgressions of the rule, while yet the unity of the group is 

 indubitable. Thus the Indian Monitor and the Inguana, though Saurians, 

 violate the second character, having an elevated coronoid process ; but 

 then it is narrow, and this seeming defect in our second character is fur- 

 ther remedied by the third ; for in those Saurians there is a depressed 

 space between the condyle and the coronoid process quite different from 

 ihat which a mammal jaw exhibits. Again, the teeth of Crocodiles^ Pie- 



