FOSSIL JAWS FROM STONESFIELD. 209 



but that double roots necessarily indicate, not the mammiferous nature of 

 the animal, but the compound form of the crowns of the teeth. 



" 2. With respect to the most prominent characters by which the Stones- 

 field fossils are distinguished from recent mammals of the insectivorous and 

 marsupial families, Mr. Ogilby mentioned, first, the position of the condyle, 

 which is placed, in the fossil jaws, in a line rather below the level of the 

 crowns of the teeth ; and he stated that the condyle not being* elevated above 

 the line in the Dasyurus Ur sinus and Thylacynus Harrisii, is not a valid 

 argument, because those marsupials are carnivorous. The second point 

 urged by the author against the opinion that the fossils belonged to insec- 

 tivorous or marsupial mammifers, is in the nature and arrangement of the 

 teeth. The number of the molars, he conceives, is a secondary considera- 

 tion ; but he is convinced that they cannot be separated in the fossil jaws 

 into true and false, as in Mammalia ; the great length of the fangs, equal 

 to at least three times the depth of the crowns, he conceives, is a strong 

 objection to the fossils being placed in that class, as it is a character alto- 

 gether peculiar and unexampled among mammals ; the form of the teeth 

 also, he stated, cannot be justly compared to that of any known species of 

 marsupial or insectivorous mammifer, being, in the author's opinion, simply 

 tricuspid, and without any appearance of interior lobes. As to the canines 

 and incisors, Mr. Ogilby said, that the tooth in D. Bucklandii, which has 

 been called a canine, is not larger than some of the presumed incisors, and 

 that all of them are so widely separated as to occupy full five-twelfths of 

 the entire dental line, whilst in the Dasyurus viverrinus, and other species 

 of insectivorous marsupials, they occupy one-fifth part of the same space. 

 Their being arranged longitudinally in the same line with the molars, he 

 conceives, is another objection, because, among all mammals, the incisors 

 occupy the front of the jaw, and stand at right angles to the line of the 

 molars. With respect to the supposed compound structure of the jaw, Mr. 

 Ogilby offered no formal opinion, but contented himself with, simply stat- 

 ing the appearances ; he, nevertheless, objected to the grooves being con- 

 sidered the impression of blood vessels, though he admitted that the form 

 of the jaws is altogether different from that of any known reptile or fish. 



" From a due consideration of the whole of the evidence, Mr. Ogilby 

 stated, in conclusion, that the fossils present so many important and dis- 

 tinctive characters in common with mammals on the one hand, and cold- 

 blooded animals on the other, that he does not think naturalists are justi- 

 fied at present in pronouncing definitively to which class the fossils really 

 belong." 



" A paper was afterwards read, entitled, " Observations on the Teeth of 

 the Zeuglodon, Basilosaurus of Dr. Harlan," by Richard Owen, Esq., 

 F.G.S., Hunterian Professor in the Royal College"" of Surgeons, London. 



" During the recent discussions respecting the Stonesfield fossil jaws, 

 one of the strongest arguments adduced and reiterated by M. de Blainville 

 and others in support of their saurian nature, was founded on the presumed 

 existence in America of a fossil reptile possessing teeth with double fangs, 

 and called by Dr. Harlan, the Basilosaurus. To the validity of this argu- 

 ment, Mr. Owen refused to assent, until the teeth of the American fossil 

 had been subjected to a re-examination with an especial view to their al- 

 leged mode of implantation in the jaw; and until they had been submitted 

 to the test of the microscopic investigation of their intimate structure with 

 reference to the true affinities of the animal to which they belonged. The 

 recent arrival of Dr. Harlan in England with the fossils, and the permis- 

 sion which he has liberally granted Mr. Owen of having the necessary sec- 

 Vol. III.— No. 29. x. s. z 



