1910.] The Hyracoidea. 363 



do not overlap any more than they do in Meniscotherium. The reduction 

 of the dio-its to 4-3 is ah'eadv suggested in Meniscotherium. The astraguhis, 

 as in Condylarths, usually lacks the cuboid facet (at least in Procavia capen- 

 sis), the cuboid lying below the level of the head of the astragalus, but in Den- 

 drohyrax arboreus an astragalo cuboid contact occurs (Osborn, 1889, pp. 

 537-538). The step-like articulation for the internal malleolar extension of 

 the tibia on the astragalus, already noted, may have been initiated from con- 

 ditions similar to those in Meniscotheriuni in which the tibia articulated 

 chiefly with the internal side of the astragalus. The pecidiar conditions in 

 Hi/rax are possibly connected with its plantigrade habits and with the de- 

 velopment of adhesive plantar pads for running up smooth steep surfaces 

 (Dobson, 1876). On the whole, however, the resemblances to Meniscothe- 

 rium do not appear to be of the same phylogenetic value as the resemblances 

 to the Proboscidea (p. 362). 



The Hyraces resemble Prott/ pother ium of the Patagonian Miocene in 

 the general form of the skull, short premaxillaries excluded from contact 

 with the frontals, backward prolongation of the malars, broad frontals 

 which strongly resemble those of the Eocene Saghatherium (see Andrews, 

 1906, pi. vii, fig. 5), high position of the squamosal root of the zygoma, 

 cancellous dilation of the squamoso-periotic, tubular upwardly directed 

 auricular meatus, shape of the posterior border of the palate and of the 

 ectopterygoid fossae, carotid canal united with foramen lacerum posterius [not 

 true of Hegetotherium and Pachyrukhos (Sinclair)], canine more or less pre- 

 molariform. The mandible also deepens posteriorly and was drawn from 

 behind upward, slightly forward and sharply inward. 



These resemblances, which do not obtain to so great a degree between 

 Hyrax and other Santa Cruz Tvpotheres are all regarded as secondary by 

 Sinclair (1908), who points out that they are associated with important 

 difl^erences in the skull, in the pattern of the molars and in the carpus and 

 tarsus (see p. 376). Nevertheless the resemblances between Hyrax and 

 Proty pother iuvi are so extraordinary that one can scarcely hel}) feeling that 

 they may after all outweigh the well marked differences above cited. 



That Dr. Andrews is right in referring to the order Hyracoidea the Eocene 

 Egyptian genera Megalohyrax and SaghatJierium appears to be indicated by 

 the following facts : 



(1) In Pliohyrax (Osborn, 1898), Megalohyrax, Saghatherium, the 

 canines are premolariform, the premolars very advanced in type, the molars 

 agree in essentials with those of Plyrax as figured by Osborn (1907, p. 185); 

 the posterior crescent of the lower molars touches the anterior crescent at a 

 point just external to the posterior metaconid spur (metastylid). In all 

 three genera the inner upper incisor (i^) is enlarged pointed, triangulnr in 

 section, as in Hyrax. 



