RHJ5TIC FORMATIONS. 3 



correspond with the then presumed exckisively Mammalian epoch, and the attempts to do 

 away with the supposed anomalous exception were afterwards confined to arguments in 

 favour of the jaw in question having belonged to a cold-blooded oviparous animal, either 

 fish or reptile. 



The grounds of such conclusion will be found in the papers by Prof. Agassiz, in 

 ' Leonhard und Bronn's Neue Jahrbuch fiir Mineralogie und Geologic,' 8vo. 1835, vol. iii, 

 p. 185 ; by De Blainville, in his " Doutes sur le pretendu Didelphe de Stonesfield," in 

 ' Comptes Rendus de 1' Academic des Sciences,' Paris, August 20th and October 6th, 

 1838; in Prof. R. E. Grant's "General View of the Characters and Distribution of 

 Extinct Animals," in 'Thomson's British Annual' for 1839; and in Mr. Ogilbt's 

 communication to the London Geological Society in December, 1838. 



The facts and arguments for the mammalian character of the fossil in question are 

 given in a paper by Prof. Valenciennes, in the ' Comptes Rendus de I'Academie des 

 Sciences,' Septembre, 1838, p. 57.2, and in my Memoir containing a description and 

 figures of Dr. Buckland's, Mr. Broderip's, and subsequently discovered specimens 

 from Stonesfield, published in the ' Transactions of the Geological Society of London ; 

 2nd series, vol. vi, pp. 47 — 65, pis. 5 and 6. 



Subsequent discoveries have not only confirmed Cuvier's conclusion, but have 

 extended our knowledge of small Mammals in Secondary strata both older and newer 

 than the Lower Oolitic one in which they were first discovered. 



The subjoined table of the earth's strata containing evidences of life shows the relations 

 to time of the first-known appearances of the warm-blooded viviparous Vertebrates (p. 4). 



To the description of these fossils, for the most part British, I now proceed. 



A. Phytic Mammals. 

 § II. Genus — Microlestes, FUeninger, 1847.^ 

 Species 1 — Microlestes antiquus, Plieninger. Plate I, figs. 14, 15, 15 a. 



In 1847 Prof. Plieninger, of Stuttgart, discovered, in sifting the sand of a 'bone- 

 bed ' in the ' Keuper ' of Diegerloch and Steinenbronn, two minute teeth, each showing a 

 well-defined enamelled tuberculate crown, supported by two distinct roots or fangs.^ 



The professor, referring to my paper on the Stonesfield jaws, in which the supposed 

 occurrence of that mammalian dental characteristic in the teeth of sharks and of the 



' " Jabresheftedes"Vereins fur Vaterliindisclie Naturkunde in Wiirtembei-g," 8vo, Bd. ii (1847), p. 164, 

 taf. i, figs. 3, 4 ; and " Nova Acta Ctes. Acad. Nat. Cur.," &c., vol. xxii (18J0), p. 902, pi. 71, figs. 14, 15. 



