436 BE. C. I. FOKSYTH MAJOK ON 



3 & 4. Lagopsis and Lagomi/s. — Since these genera have five cheek-teeth in both jaws, 



there being a small fifth inferior tooth, their tooth-formula will be : — 



p 3 ^ 2 p. 3, p. 2, p. 1 ; m. 1, m. 2 



2 3 p. 2, p. 1 ; m. 1, m. 2, m. <i 



To sum up. The nvimber of premolars is constant in all the genera of Lagomyidye, 

 and the same as in Lepus ; whereas that of the true molars varies in the different genera ; 

 not rice versa, as has been supposed by Lydekker *, Flower f, and Zittel %. 



The iipper m. 3, always present in Lepus, is always absent in the Lagomyidte. Of the 

 lower true molars, m. 3 is always present in Lagopsis and Lagomijs, when not lost in the 

 fossil : it is always absent in Prolagm ; while in TUanomys this tooth is rarely absent 

 in one species, T. Fontannesi, more frequently in the other, T. visenoviensis, but presumably 

 always present in young specimens of both. 



1. Genus Titanomys. 



TUanomys, H. v. Meyer, Neues Jahrb. 1843, p. 390. 



Lagodus, Pomel, Cat. meth. Vert. foss. Loire et Allier, p. 41 (1853) ; Deperet, Arch. I\Iits. Lyon, iv. 



p. 12(5 (1887). 

 Lagomys (subg. Amphilagus), Pomel, op. cit. p, 42. 

 Lagomys, Lydekker, Cat. Foss. Mamm. Br. Mus. i. p. 255 (1885). 

 Lagomys (Lagopsis), Schlosser, Pal. Oestr.-Ung. viii. p. 8fi, foot-n. 4 (1890), p.p. ; Deperet ?, Arch. Mus. 



Lyon, V. p. 58 (1892). 



Titanomys visenoviensis. 



Titanomys visenoviensis, H. v. Meyer, Neues Jalirb. 1843, p. 390; Gervais, Zool. et Pal. fr., prem. ed., 

 Expl. No. 46, pi. xlvi. fig. 2 (1848-52) ; Bronn, Lcth. Geogn. iii. p. 103 (1853-56) ; Gervais, Zool. 

 et Pal. fr., deux, ed., p. 50, pi. xlvi. figs. 1, 2 (1859); H. v. Meyer, Palieontogr. xvii. p. 225, 

 pi. xlii. (1870) ; Filhol, Ann. Sc. Geol. x. p. 26, pi. ii. figs. 25, 26, pi. iii. figs. 1-18 (1879) ; 

 Schlosser, Palaontogr. xxxi. p. 29, pi. xii. figs. 36, 38, 39, 41, 43, 45, 47, 48 (1884) ; Zittel, Handb. 

 d. Palajont. i., iv. p. 552 (1891-93). 



Titanomys trilohus, Gervais, Zool. et Pal. fr., prem. ed., Expl. No. 46, pi. xlvi. fig. 1 (1848-52). 



Lagodus picoides, Pomel, Cat. meth. p. 41 (1853). 



Lagomys (subg. Amphilagus) antiquus, Pomel, op. cit. p. 43. 



Ampkifagus antiquus, Schlosser, op. cit. p. 30. 



Lagomys visenoviensis, Lydekker, Cat. Foss. Mamm. Brit. Mus. i. p. 258 (1885). 



Sistorical Sketch. 



In announcing his new genus Titanomys (type species T. visenoviensis), from the Lower 

 Miocene of Weisenau near Mayence, H. v. Meyer characterizes it as having prismatic 

 cheek-teeth, agreeing in size and number and resembling in form those of Lagomys, 

 with the difference, however, that the lower molars of the fossil present a distinct 



* Cat. Foss. Mamm. Br. Mus. i. p. 255 (1885) ; Nicholson & Lydekker, Manual of Palseont. ii. p. 1412 (1889). 



t Flower & Lydekker, ' Introduet. to the Study of Mammalia,' p. 491 (1891). 



t Zittel, Handb. d. Pala30nt. i., iv. p. 551 (1891-93); id. Grand;!, d. Paloeont. p. 825 (1895). 





