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It is a matter of considerable regret to me, that before concluding 

 my notice of the Perissodactyla, I am again compelled to differ from 

 that high authority to whom we owe so much, and in whose footsteps 

 I may here be said, as it were, to follow. Although I am prepared 

 to show that the evidence of the teeth, on which Prof. Owen decided 

 the place of his genus Hyracotherium, is not so strong as it may 

 appear ; yet, on the other hand, their resemblance to those of the 

 group to which I must transfer it is not so striking as to have caused 

 me in the least to doubt the correctness of the place assigned to it, 

 imtil I was well satisfied of the value of the cranial characters which 

 I have pointed out. Although the true molars resemble those of 

 the Choeropotamvs and other non-ruminant Artiodactyla in the tuber- 

 cular form of the four principal eminences, and in having the ridge 

 surrounding the base more complete than is usual in the Perisso- 

 dactyla, yet to make the resemblance good, they should have, in 

 addition to the two smaller tubercles, the one in the front, the other 

 in the middle of the tooth, a third one behind ; and the fact is well 

 worthy of attention, that each of these secondary tubercles is placed 

 upon the angle of a bent ridge which connects the pair of larger ones 

 immediately behind it, and which in the smaller species {Hyracothe- 

 rium Ciiniculus) exists, while the little tubercle itself is wanting ; thus 

 showing that the ridge is a more essential part of the tooth than the 

 tubercle developed upon it ; and this ridge just marks out in a rudi- 

 mental way the bent transverse ridges in the Rhinoceros, Tapir, Pa- 

 Iseotherium, and other allied genera. The two last premolars differ 

 from the true molars only in the non-development of the inner tubercle 

 of the posterior pair, but of which a slight rudiment is still traceable ; 

 and the sudden change of form between these teeth and the two first 

 is met with in no other genus, either of the Artiodactyle or Perisso- 

 dactyle group. This would be perfectly in accordance with law, if 

 the third and fourth molars belon2:ed to the milk series, and the ani- 

 mal were Artiodactyle ; but the whole series has the appearance of 

 adult completeness, and neither the form nor the degree of wear of 

 these teeth at all indicates such to be their nature ; — indeed Prof. 

 Owen himself never once hints at such an idea. To whichever group, 

 then, this little animal be referred, the teeth will present marked ex- 

 ceptional characters, and therefore it becomes more necessary to seek 

 for further evidence. I was first led to suspect a Perissodactyle affi- 

 nity, through observing, by the figures and description pubhshed in 

 Prof. Owen's very useful work on the British Fossil Mammalia, that 

 the nasal bones exhibit the character of this group in a very decided 

 manner, and that the supraorbital foramen and groove are entirely 

 wanting. This induced nie to examine with care the unique speci- 

 men in the Museum of the College of Surgeons, and I thus con- 

 firmed these characters, and also found that the mark indicating the 

 origin of the obliquus inferior oculi is but a slight depression, not 

 more marked than I have seen it in some skulls of Rhinoceros and 

 Hyrax, and not placed in a fossa, but simply upon the general uni- 

 form concavity. Although the posterior portion of the skull is en- 

 tirely lost, yet enough remains to show that there was but a slight 



