FOSSIL AND EECENT LAGOMOEPHA. 443 



ni. 2 in its j)Ostero-exterual portion (compare fig. 19, PI. 36, with fig. 6) ; so that the choice 

 remains only hetweeu p. 1 and m. 1. It resembh's closely the p. 1 described ; only it is 

 narrower, and the anterior lobe of the latter is more developed in its internal portion, 

 althongh the inverse w"as to be expected, tlie p. 1 described being less worn. For tliese 

 reasons I think it more likely to be m. 1. This tooth shows tw'o small roots on the outer 

 side ; on the inner side the crown gradually thins out downward into a single large root. 

 It cannot be a milk-tooth, because the two small external roots do not diverge downwards, 

 but run parallel with each other. We have here another proof, if one were needed, that 

 in Titanomys visenomeiisis the upper teeth are provided with roots ; although this fact 

 has been denied with regard to this species of the Lower Miocene. 



Mandibular teeth of Titanomys visenoviensis. — As a characteristic feature of the lower 

 cheek-teeth of T. visenovietisis, II. v. Meyer makes mention of a small posterior lobe, 

 calling it a distinct posterior appendage (" ein dcutlicher Hinteransatz ") *. About the 

 occurrence of this small particle much uncertainty prevails. When establishing the 

 genus, in the paper just quoted, H. v. Meyer mentioned it in a general way as present in 

 the lower cheek-teeth, seemingly implying that all of tliem were provided with this 

 appendage. In his posthumous memoir, however, speaking again of the Weisenau speci- 

 mens, he says that it occurs on Win posterior cheek-teeth and would have disappeai'ed by 

 effect of attrition t- Pomel assigns it to the three posterior cheek-teeth of " Lagodus 

 jyicoides," adding that it takes its origin from the internal angle, that it is more evident 

 especially in the last molar and disajjpears rather late by attrition |. 



According to Gevvais § it would occttr only on the fourth tooth (m. 2), and as a character 

 of young specimens ; the same is stated by Filhol || , who had at his disjjosal a considerable 

 number of lower jaws. Schlosser ^ styles it a third lobe occttrring as an anomaly 

 (" abnorm vorkommend ") in "m. 3" (meaning m. 2) of Titanomys visenoviensis; 

 although in the same memoir he figures manuscript drawings by H. v. Meyer, wdiere 

 it is shown in two molars. This same small lobe occurs in Palceolaff/is also; it is 

 transitional in one species, P. Haydeni, as described l)y Cope **, apparently persisting 

 in another sjiecies, P. triplex ff. On a former occasion I incidentally pointed out the 

 interest attached to it from both a phylo- and ontogenetic point of view J J. 



As to the occurrence of this small lobe or cusp in T. visenoviensis, my own observations 

 tend to show that it is constantly present in young specimens, not only of the posterior, 

 but also of the anterior lower teeth, including p. 2. In a fragment of a right 

 mandibular ramus of T. visenoviensis from the Allier (Bravard Collection, Br. Mus. 

 31094-104), PI. 37, fig. 25, exhibiting the two anterior cheek-teeth, p. 1 and p. 2, in a 

 moderate stage of wear, traces of this iol)e are visible in both these premolars, very 

 distinctly in the posterior (p. 1). 



* Neues Jabrb. 1S43, p. 390. t Talicontogr. xvii. p. 226 (1870). 



+ Cat. nn'-th. p. 41 (1853). § Zool. ct Pal. Franc;, sec. ed. p. 50 (1859). 



i; Ann. Sc. C4l:o1. x. p. 27 (1879). If Pala-ontograph. xxxi. p. 32 (1884). 



** ' The Yerteljrata of the Tertiary Formations of the West," p. 876 (1883). 

 +t Op. cii. p. 881. Ji Proc. Zool. 8oc. London, p. 203 (1893). 



62* 



