J8S9.] SPECIES OF HYRACODONTOTHERIUM. 69 



in the former the space occupied by the four premolars exceeds that 

 between the caniue and the anterior border of the first incisor by the 

 whole width of the latter, in the present specimen the first of these 

 dimensions only slightly exceeds the second. Again, whereas in 

 the type species the first premolar is not longer (antero-posteriorly) 

 than the canine, and is much shorter than pm. 3 , iu the present 

 specimen the length of pm- 2 is much greater than that of the canine, 

 and its difference from that of pm. 3 less than in the type. Further, 

 there is a larger interval between ijj2 and ^3 in the specimen under 

 consideration. 



These differences are indicated by the following measurements : — 



H. primarvum. H. filholi. 



Ant.-post. diam. of ij^ 0,006 0,011 



Transverse „ „ 0,006 0,010 



Ant.-post. diam. of canine 0,007 0,00S 



pm.l 0,007' 0,009.5 



pm- 2 0,009' 0,010 



Length of space occupied by premolars . . 0,030 0,039 

 Interval between canine and anterior border 



of ij 0,022 0,035 



Length of outer narial border 0,023 0,038 



Interval between i^ and i_3 0,003 0,007 



There is of course the possibility of these differences being sexual 

 rather than specific, in which case the present specimen would be 

 the male, and the increase in the first incisor would be analogous to 

 that of the canine in the male Pig. In the absence, however, of any 

 known instance, except iu the case of the Elephant, of such a difference 

 in the incisors of the two sexes, I am disposed, at least provisionally, 

 to regard the present specimen as indicating a second si^ecies of the 

 genus, which may be known by the name of H. filholi. 



The present specimen is important as showing that pm. 4 differs 

 from that oi Meniscotherium in having only a single outer lobe. 



"Whether the resemblance of the anterior portion of the skull of 

 nyracodontotherium to Hyrax indicates a genetic relationship between 

 the two forms, the evidence at present available is insufficient to de- 

 cide. It is, however, significant that both the Hyracoidea and the 

 Condylarthra have such a similar type of carpus and tarsus that they 

 are bracketed together by Prof. Cope in a single group. It may be 

 added that the presence of an entepicondylar foramen in the humerus 

 of Meniscotherium is in favour of Cope's reference of that genus to 

 the Condylarthra rather than to the Perissodactyla. 



Finally, I have to thank Dr. H. Woodward for permission to 

 bring the sjiecimen forming the subject of this communication under 

 the notice of the Society. 



^ These dimensions are taken from Dr. Filhol's figure, and differ somewhat 

 from those given in the text. 



