282 Mr. K. Andersen on the Dnts 



the maxillar tooth-roAV ; median anterior point opposite front 

 of ni^, median posterior point level with middle of m^. 

 Basioccipital not unusually narrowed. 



In Rh. arcuatus the premolars and molars are compara- 

 tively small, the temporal fossa narrow ; the zygomatic 

 breadth of the skull, therefore, practically the same as the 

 mastoid breadth ; the sagittal crest low, very gradually 

 passing into the sujjraorbital ridges. Rh. euryotis shows the 

 other extreme : the larger teeth have caused a stronger 

 development of the temporal muscle, a widening out of the 

 temporal fossa, therefore a markedly larger zygomatic width 

 of the skull, a heightening of the sagittal crest, especially in 

 front, making the declivity of this latter towards the post- 

 nasal depression more abrupt ^. These two extremes are 

 connected together by several intermediate stages. 



Teeth. — Throughout the whole group the dentition is 

 rather uniform. All the species have passed the primitive 

 stage : p^ in the tooth-row, this premolar being invariably 

 external to the row, when not completely wanting. As a 

 general rule, pc, andjo^ are in contact, not rarely so strongly 

 so that their cingula overlap each other ; but sometimes 

 individuals occur in w hich p^^ and jh ^i'<3 distinctly separated, 

 reminiscent of the time whenjWg was situated in the tooth- 

 row. The upper p^ is small and always in row. 



Nose-leaves. — Chief characters : the shape of the sella and 

 the connecting-process. 



The sella is approximately ovate or ovate-pyriform. The 

 connecting-process strongly arcuate, almost semicircular in 

 outline, and starting from the very summit of the sella. 

 The internasal lobes slightly larger than usual in the genus. 

 The sella is peculiarly modified in Rh. inops, the connecting- 

 process in Rh. Creaghi. 



There are two well-marked " types " of horseshoe in this 

 group. In the more primitive species the median longitudinal 

 groove separating the two halves of the horseshoe in front is 

 narrow (linear) ; in the higher developed forms it is broad, 

 more or less pentangular in shape. The former condition is 

 characteristic of the species inhabiting the Philippine Islands 

 and N.E. Borneo [arcuatus, subrufus, inops, Creaghi), the 

 latter of the forms distributed over Batchian, Amboina, 

 Timor Laut, and the Key Islands [euryotis and its local 

 representatives) . 



* For similar cranial differences in the Bh. j^hilippinensis group, see 

 Ann. & Mag. Nat. Hist, for August 1905, p. 245. 



