Vol. 70.] YERTEBKATES FROM BEITISH EAST AETJICA. 177 



valley, a structure not seen in the specimens examined. Prof. H. F. 

 Osborn l considers that the sub-family — the Ceratorhinse — to which 

 Rhinoceros schleiermaclieri belongs first appears in the Middle 

 Miocene of Europe, where it is represented by JRJi. sansaniensis. 

 Dr. L. Mayet, 3 on the other hand, carries the line back to 

 JRh. tagicus Roman, from the Burdigalian Beds of Portugal. If 

 further discoveries confirm the relationship of the species here 

 described with ~Rh. schleiermacheri, it would seem that a probably 

 African origin may be assigned to the Ceratorhinae, but much 

 more material is necessary before any conclusion can be drawn. 

 The dimensions (in centimetres) of this tooth are : — 



Greatest width of the crown at the base 6'5 



Greatest length of the crown 5*6 



A portion of the upper part of the radius shows that it was not 

 fused with the ulna, and that the limb was probably not very 

 heavy. A left os magnum and a left cuboid are also included 

 in the collection. 



Order RODENTIA. 



This order is represented by a fragment of the left ramus of the 

 mandible (PL XXVIII, fig. 7) of an animal almost as big as 

 a guinea-pig ; the fourth premolar and the first and second molars 

 are in situ. This specimen is from Bed 24 at Kachuku. 



The teeth are brachyodont, and each molar consists of two outer 

 heart-shaped cusps (protoconid and hypoconid), the external angles 

 of which are directed forwards — the two being separated by a deep 

 groove directed somewhat backwards. The inner face of the tooth 

 bears two cusps, the metaconid and the entoconid : of these the 

 former is connected with the protoconid by a ridge which forms 

 the anterior wall of the tooth-crown. The entoconid is connected 

 by a ridge crossing the middle of the crown to the inner point 

 of union of the wear-surfaces of the antero-external and postero- 

 external cusps. At the bottom of the bay between this transverse 

 ridge and the anterior wall of the tooth is a slight prominence, 

 apparently the rudiment of another transverse ridge. Finally, the 

 postero- external cusp is connected with a ridge forming the hinder 

 wall of the crown (hypoloph) ; this turns strongly forwards at its 

 inner end, and in wear would become connected with the postero- 

 internal cusp (entoconid), enclosing an enamel-covered valley. The 

 enamel on the outer side of the external cusps is very thick, but 

 the internal cusps are the most prominent. 



The premolar, so far as its posterior half is concerned, is similar 

 to the same part of the molar ; but the anterior region is reduced, 

 and appears to consist of one large cusp or (perhaps, more properly) 



1 Bull. Am. Mus. Nat. Hist. vol. xiii (1900) p. 256. 



2 ' Etude des Mammiferes Miocenes des Sables de l'Orleanais ' Ann. Univ. 

 Lyon, n. s. Sciences, fasc. xxiv (1908) p. 113. 



