444 DE. C. 1. FOESYTH MAJOR ON 



It has been found convenient to give the detailed descriptions of the lower molars of 

 this and all the other genera in a separate chapter (p. 473). 



TiTANOMYS FONTANNESI. 



Lagodus Fontannesi, Deperet, Arch. Mus. Lyon, iv. p. 127, pi. xiii. figs. 19-19 c (1887). 

 Lagomys [Lagopsis) verus, ScLlosser, Pal. Oestr.-Ung. viii. p. 86 (1890) ; Deperet (?), Arch. Mus. Lyon, 

 V. p. 57 (1892). 



Under the name of Lagodus Fontannesi, Deperet described a fragment of an ixpper 

 jaw, from the Middle Miocene of La Grive-Saint-Alban (Isere), as related to Titanomys 

 visenomcns-is, H. v. Meyer ; but, in addition to its larger size, he distinguished it by other 

 more important characters. 



Schlosser has sup2)osed, without assigning reasons, that Lagodus Fontannesi, Dep., is 

 synonymous with Lagomi/s {Lago2)sis) verus, Hens. {^Lagomys oeningensis, H. v. Mey.), 

 and Deperet, in his second publication on the Fauna of La Grive, is disposed to accept 

 Schlosser's views. It may be asked at once, Avhat then becomes of the left palate, 

 figured and desci-ibcd by Deperet in his first memoir *, where he considers it, rightly in 

 my opinion, to belong to the Lagomys rerus. As this question will be discussed under 

 the head of Lagopsis verus, when it will be shown that Deperet's original view in 

 distinguishing between " Lagodus Fontannesi " and Lagomys verus is the correct one, 

 we have for the present only to deal with Deperet's first memoir, in which " Lagodus 

 Fontannesi" is described, and where he asserts that it is distinct as a genus from 

 Titanomys viseno^iensis of the Lower Miocene. 



For this Deperet gives two reasons. In the first line he maintains that his Lagodus 

 preserves in its adult dentition part of the characters of the deciduous dentition of 

 Titanomys visenoviensis, meaning that in the latter the milk-teeth alone are rooted, 

 while in the former the permanent cheek-teeth arc rooted as well. I have already 

 disposed of this supposed difference, by showing that the permanent teeth of Titanomys 

 nisenovicnsis are likewise rooted. 



Deperet's second reason is given in the following words : — " Le Lagodus Fontannesi 

 se distingue d'ailleurs facilement du Titanomys visenoviensis . . . par quelques differences 

 dans les dessins d'email qui ornent la surface de la couronne " (i. e. of the upper molars). 

 " D'apres M. Filhol, le lobe posterieur des molaires superieures du Titanomys d'Auvergne 

 est orne d'un double pli en chevron entourant une pointe externe ; dans le Lagodus de 

 La Grive il y a trois plis en chevron concentriques et pas de pointe exterieure bien 

 manifeste"t. 



The enlarged figures of the triturating surface in the teeth of "Lagodus Fontannesi" 

 and Titanomys riseiioviensis do not help us, as they are sadly inaccurate. The artist who 

 drew the former J completely failed to understand the pattern ; while in Filhol's enlarged 

 drawings § the artist has not even made an attempt at accuracy, contenting himself 

 with drawing the outlines of the teeth, and leaving out almost completely the details of the 



* Arch. ilus. Lyon, iv. p. 104, jil. xiii. tig. 17 (1SS7). 



t Op. cit. p. 128. i Op), dt. pi. xiii. fig. 19 b. [§ Op. cit. pi. iii. fig. 15. 



