HTEACOIDEA. 83 



Suborder HYRACOIBEA. 



Ungulates with plantigrade feet and a centrale in the carpus. The axis of the limb 

 passing through the third digit ; the first and fifth digits reduced in varying degrees. 

 The radius and ulna complete and separate, at least in the young. No entepi- 

 condylar foramen in the humerus, and no clavicle. The femur with a small third 

 trochanter; tibia and fibula complete and separate, at least in the young; fibula 

 articulating with astragalus. The dentition heterodont and diphyodont. In the 

 earlier forms here described the full eutherian dentition is present, and the premolars 

 are simpler than the molars; in the later forms the dentition is more or less reduced 

 by the loss of the canines and some of the incisors, and the posterior premolars 

 at least are molariform. In all the anterior pair of upper incisors are enlarged and 

 grow from a persistent pulp. 



Till within the last few years this remarkable and very isolated group of Ungulate 

 mammals was quite unknown in the fossil state. In 1898, at the Cambridge Meeting 

 of the International Zoological Congress, Professor H. F. Osborn read a short paper on 

 a skull from the Lower Pliocene of Samos in the Stuttgart Museum, which he showed 

 to have belonged undoubtedly to a large Hyracoid, to which he gave the name 

 Pliohyrax kruppi. This paper, illustrated by a plate, was subsequently published 

 in the Proceedings of the Congress. Osborn regarded Pliohyrax as being an 

 aquatic or semi-aquatic form. It possesses three pairs of upper incisors, the first 

 being large trihedral teeth, much as in the later forms. The others are in contact 

 with one another and with the canine, so that the molars, premolars, canine, and the 

 two incisors on either side form a continuous series. Meanwhile Schlosser * pointed 

 out that a mandible with the cheek-teeth from the Lower Pliocene of Pikermi, described 

 by Gaudry under the name of Leptodon grcecus, is in fact also a Hyracoid, and he 

 drew attention to an almost complete lower jaw from Samos preserved in the 

 Paleeontological Museum at Munich. This specimen Schlosser considered to belong 

 to the same species and possibly even to the same individual as the Stuttgart skull 

 described by Osborn. Still later, Dr. Forsyth Majorf described another skull from 

 Samos, preserved in the British Museum, regarding this as also belonging to Gaudry's 

 species, which he showed must be called Pliohyrax grcecus, the name Leptodon grcecus 

 having the priority, but the generic term Leptodon having been previously employed. 



* Schlosser, " Ueber neue Funde von Leptodon grcecus, Gaudry, und die systematische Stellung dieses 

 Saugethieres," Zool. Anzeig. xxii. (1899) pp. 378 and 385; A. Gaudry, ' Animaux Fossiles et Geologie de 

 I'Attique,' 1862, p. 215, pi. xxxiv. figs. 1, 2. 



t Forsyth Major, " The Hyracoid, Pliohyrax grcecus (Gaudry), from the Upper Miocene of Samos and 

 Pikermi," Geol. Mag. [4j toI. vi. 1899, p. 647. 



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