UYRACOIDEA. 
83 
f 
Suborder IIYRACOIJJEA. 
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 wuthin 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 Jcmppi. 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 Low^er 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 
Palaeontological 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 Major f 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 Ruude von Leptodon grcecus, Gaudry, und die systematische Stellung dieses 
Saugethieres,” Zool. Anzeig. xxii. (1899) pp. 378 and 385; A. Gaudry, ‘ Animaux Fossiles et Gdologie de 
I’Attique,’ 1862, p. 215, pi. xxxiv. figs. 1, 2. 
t Forsyth Major, “The Hyracoid, Pliohgrax grcecus (Gaudry), from the Upper Miocene of Samoe and 
Pikermi,” Geol. Mag. [4] vol. vi. 1899, p. 547. 
M 2 
