4i0 DE. C. I. FOESTTH MAJOE ON 



teeth were formed as in Lagomys. This evidently implies that they have no roots ; for 

 the writer proceeds to state that in the teeth anterior to those just mentioned lengthened 

 roots can be seen. In the two anterior cheek-teeth of the lower jaw, H. v. Meyer 

 describes a short crown and a long root, composed of two strongly converging parts; 

 and these two teeth seem to be situated somewhat higher than the two posterior, which 

 suggests that they had not yet emerged above the alveolar margin. Contrary to the 

 anterior rooted teeth, these two posterior ones are described as " prismatic " ; the whole 

 of their crown has an enamel coating, and is not completely closed below. The author 

 concludes that the teetli seem to indicate that the animal was of immature age, a 

 supposition which would explain the differences of the anterior teeth from those of 

 Jjagomi/s. 



As a matter of course, in the lagomorphoiis Rodentia with permanent cheek-teeth 

 growing by persistent pulj)s, the deciduous teeth are rooted too as in the Rott skeleton. 

 But the author proceeds to state (p. 128) that he has examined detached teeth of the 

 Titanomijs from Weisenau of two kinds : on the one hand, small teeth corresponding to 

 the anterior teeth of the Rott specimen ; on the other, lower teeth ditfering from the 

 last by a lengthened prismatic crown and quite insignificant roots ; and upjDer teeth 

 as well, of larger size than those corresponding to the U2:)per anterior teeth from Rott, 

 supposed by H. v. Meyer to be possibly deciduous. In the larger teetli the roots are 

 said to disappear almost comjdetely ; " die flach prismatisohe, gekrummte Krone vertritt 

 zugleich die Hauptwurzel, und es wird nur aussen oben ein kleines "Wiirzelchen wahrge- 

 nommen, das audi in einer entsprechenden Stelle des Kiefers eingrcift, wahrend das an 

 der Innenseite mit einer Rinne versehene Zahnprisma die eigentliche Alveole ausfiillt." 



Prom what will be seen later on, these larger teeth, upper and lower, are in fact the 

 permanent teeth of Titanomys, as H. v. Meyer hesitatingly suggests. Therefore there is 

 no foundation in the distinction — such as is drawn by Deperet — of two genera, founded 

 on the presence or absence of roots in the permanent teeth, viz. : — 



(1) Titanomys, with roots in the deciduous set only. 



(2) Lagodus, with roots in the permanent teeth as well (premolars and true molars). 

 Proceeding with our historical sketch in chronological order, we next have to 



consider Filhors descrij)tion of Titanomys cisenoviensis from Saint-Gerand-le-Puy 

 (AUier) *, which has already been quoted more than once in the preceding pages. 

 Among the synonyms of this species are given Ariiphilagus antiquus, Pom., and 

 Lagodus pico/des, Pom. : the identification of the former rests on one of the type 

 specimens of Pomel ; the latter is not discussed in the paper. An important character 

 noted by Filhol is the relatively considerable longitudinal extension of the bony 

 palate in Titanomys. The shortness of the bony palate in lagomorphous Rodents is 

 doubtless a specialization ; but by its greater extension Titanomys approaches more 

 the condition of other Ptodentia and Mammalia generally. The same is true of 

 Falcpolagus, from the Miocene of North America, which presents curious resemblances 

 with Titanomys in its dentition also. Moreover, we meet with a lengthened bony 



* Ann. Sc. Geol. x. p. 26 (1879). 



