370 Dr. C. I. Forsyth Major — 8ome Rodents from Oeningen. 



the diastema between the anterior premolars and the incisoi's is 

 longer than in Zagopsis, and the inferior outline of the ramus, 

 when viewed from the external side, is straighter in Titanomys. 



Of upper cheek-teeth, which I feel entitled to ascribe to Zagopsis 

 verus, I have found two amongst the fossils of La Grive (Brit. Mus. 

 Geol. Dep., M. 5,264). The median of the three upper premolars of 

 the recent Zagomys, p. 2, is characterized by a crescent enamel- 

 folding, which opens freely on the outer margin of the tooth, near its 

 anterior angle.' Zagopsis being the one Tertiarj' genus which in 

 the form of its lower teeth comes nearest to Zagomys, it might be 

 anticipated that the upper teeth of the fossil would likewise show 

 a near approach to the recent Zagomys. In fact, one of the isolated 

 teeth just mentioned, from La Grive, exhibits the same somewhat 

 triangular outline, the apex being turned outwards, as the second 

 upper pi'emolar of Zagomys, and about the same characteristic enamel 

 folding. It can therefore with certainty be determined as p. 2 of 

 Zagopsis ; I have described and figured it elsewhere. It can at 

 once be distinguished from p. 2 of Prolagus Oeningensis (Kon.), 

 occurring in the same deposits : in P. Oeningensis this tooth is much 

 smaller, has a triangular outline with tlie apex turned inwards, 

 and has a second enamel crescent, smaller than the one corre- 

 sponding to the single one in the tooth of Zagopsis, and situated 

 externally to it. The upper p. 2 of Titanomys Fontannesi, which 

 approaches nearer in size to Zagopsis, though slightly smaller, is 

 provided with roots, and, besides, presents other differences which 

 are referred to in my memoii*. 





JWj 



9-^ 



P-i 



f A ' 



n^.z. 



n-^.i. 



Fig. 1. — Triturating surfaces of the three upper premolars, right side, of Znc/opsis 

 rents (Hensel), much enlarged; from the specimen No. 42,815 in the 

 British Museum, Geological Department. 



Fig. 2. — The median premolar, p. 2, of same, from behind, much enlarged. 



a, internal enamel folding ; h, enamel crescent ; c, enamel ring ; 6, cusp, 

 separating b and c ; 8, antero -internal cusp ; 9, postero-iuternal cusp. 



We know, then, from La Grive, a deposit contemporaneous with 

 Oeningen, apart from the small Prolagus Oeningensis, two larger 

 lagomorphous Eodentia, both of approximately equal size. It is 



1 See R. Hensel in Zeitschr. deutsch. geol. Ges., Yiii, pi. xtI, figs. 1-3 (185(5). 



