462 UE. C. I. rOESTTH MAJOR ON 



figured in fig. 31 can at once be distinguished ; the former is much smaller, has a tri- 

 angular outline with the apex turned inward, and a smaller enamel crescent (c), smaller 

 than, and external to {b). The upper teeth of Titanoijii/s Fontannesi, which in size 

 come nearer to the original of fig. 31, though slightly smaller, are provided with roots, 

 and they present other differences which have already been described. Prom its 

 resemblance to Lagomys this tooth (fig. 31) can therefore with certainty be determined 

 as belonging to Lagojjsis vents. The second of the isolated teeth before mentioned, from 

 LaGrive (PI. 36. fig. 32), agrees in size with the first; and for this reason alone Prolagiis 

 ceniiigensis can be excluded. It is either p. 1 or m. 1, if we judge from its agreement 

 Avith the corresponding teeth in Lagomys. 



In the Palaeontological Collection of the British Museum (No. -12815) is preserved a 

 slab from ffiningen, showing the skeleton, " in a much crushed and imperfect condition," 

 of a lagomyid Rodent, which Lydekker has determined as Lagomys amingensis, H. v. 

 Mey., because it agrees very closely in size with that figured by H. v. Meyer on pi. iii. 

 fig. 1 of his ' Possile Saugethiere von (Eningen ' *. On examination of this specimen 

 (No. 42815) several cheek-teeth are seen in a fragment of the cranium, presenting their 

 inner sides, the bone being here broken away. The lower parts of these teeth, in tlie 

 neighbourhood of the crowns, as Avell as these, were hidden in the matrix when the 

 specimen came into my hands. By carefully removing the matrix, the triturating 

 surfaces of the three anterior cheek-teeth (the three premolars) uere l;nd bare, and 

 it became at once apparent that this fossil is a Lagopsis. 



It w^as too late to have the teeth figured in the present memoir, so that I must 

 content myself with their description. I give figures of them elsewhere t- The posterior 

 of the three teeth (p. 1) exhibits the pattern, which is shown by the homonymous premolar 

 of Lagomys and by the latter's two true molars. On the outer side of this tooth is a 

 shallow and open groove, which, so far as can be made out under a strong lens, has no 

 enamel border. Prom the middle of the inner margin a lozenge-shaped narrow enamel 

 fold [a of my figures in PI. 36) runs transversely across two-thirds of the breadth 

 of the triturating surface towards the outer side ; the posterior enamel border of this 

 fold is raised into a strong crest, running parallel with the anterior enamel border of 

 tbe tooth, both presenting a slight convexity turned anteriorly. The enamel fold is 

 filled with cement in its outer narroAver portion, its wider internal ojiening being devoid 

 of this substance. 



The pattern of the middle premolar, p. 2, proves that the isolated tooth from La Grive 

 (PL 36. fig. 31) has been rightly determined as p. 2. As in the latter and in Lagomys^ 

 there is only a comparatively shallow internal enamel fold {a) jiresent in the tooth 

 from CEningen, the greater part of the triturating surface being occupied by the enamel 

 crescent {h) before described in the tooth from La Grive. Outside the crescent (i) 

 appears a small enamel ring filled, like the latter, with cement ; this ring is doubtless the 

 vanishing homologue of the outer enamel crescent [c) of T/^^'«o;«y.s and Pro^^^MS, described 

 in the preceding pages and figured in PI. 36. In the La Grive specimen (fig. 31) there is 



* Catalogue of the Fossil Mammalia iu the British Museum (Natural History), i. p. 250, No. 42815 (1885). 

 t Geol. Mag., dec. iv. vol. vi. p. ;J70, figs. 1 & 2 (1890). 



