1889.] SPECIES OF HYRACODONTOTHERIUM. 69 
in the former the space occupied by the four premolars exceeds that 
between the canine 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, in 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 i-2 and i.3 in the specimen under 
consideration. 
These differences are indicated by the following measurements :— 
ET. primevum. H. filholi. 
Ant.-post. diam. of 1) .............. 0,006 0,011 
Transverse ,, - BEN epetsu tt eis.0 (asters 0,006 0;010 
Ant.-post. diam. of canine .............. 0,007 0,008 
POW A i ar 0,007 0,0095 
. a ce Aes nM | 01 0,010 
Length of space occupied by premolars .. 0,030 0,039 
Interval between canine and anterior border 
ofp ee 0,022 0,035 
Length of outer narial border .......... 0,023 0,038 
Interval between i. 2andi.3 1... 2.4... 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 in 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 species 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 of Meniscotherium in having only a single outer lobe. 
Whether the resemblance of the anterior portion of the skull of 
Hyracodontotherium 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 specimen 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. 
