362 Bulletin Amerian Museum of Natural History. \yo\. XXVII, 



base of the Ungulate series than any other livhig form, except the Elephant, 

 there is as it were a hesitation to adopt definitely the form of the azygos 

 veins to be seen in either Artiodactyle or Perissodactyle." 



The Hyraces resemble the Rodentia chiefly in the purely adaptive char- 

 acter of the enlarged incisors and diastema and in the above noted characters 

 of the fundus oculi. They resemble the Amblypoda and Proboscidea in the 

 width of the vertebral centra, arched back, high number of dorsals, flattened 

 ilium (which might give rise to the spreading type), long humerus and femur, 

 stout ulna, partial crossing of the radius and ulna, short digits and flattened 

 carpals. They further resemble the Proboscidea in certain characters of the 

 fundus oculi, in the zonary placenta, in the flat nail-like characters of the 

 hoofs, in the small lachrymal, in the extension of the malar to the glenoid 

 fossa, in the lack (cf. Insectivores) of posterior clinoid processes in the pitui- 

 tary fossa (FloM'er), and finally in the reduction of the floccular fossa of the 

 petrosal (Flower). Special resemblances to Mceritherium are noted below 

 (p. 368). 



These resemblances are consistent with the hypothesis that the Hyra- 

 coidea and Proboscidea, together with certain other groups (p. 110) have 

 been derived from unknown basal members of the Condylarth-Amblypod 

 stem. 



Resemblances to different Perissodactijla are numerous. The Perisso- 

 dactyl features of the fundus oculi have been noted above. The ossicula 

 auditus suggest those of the horse (Doran, 1879), and so also the Eustachian 

 tube, especially the peculiar diverticulum from it (Weber, 1904, p. 711). 

 The mastoid portion of the periotic is reduced and the molar pattern, which 

 is buno-lopho-selenodont, has a Perissodactyl-like facies, especially in 

 Megalolii/rax minor (x\ndrews, 1906, pi. vii, fig. 1) in which the true molars 

 suggest those of Palceosyops. The premolars also tend to become like the 

 molars, but differ in details from those of any known Condylarth or Perisso- 

 dactyl. The lower molars of Megalokijrax (Andrews, op. cit., pll. vi, vii) 

 have a reduplicate metaconid, as in Meniscotherium, Eohippus, Lamb- 

 dotherium, etc., and the hypoconulid is small. The digits are reduced to 

 four in the manus (a reduced hallux sometimes persists) and three in the pes, 

 as in Lower Eocene Perissodactyls. All the foregoing characters as well as 

 the arrangement of the chief cranial foramina, seem consistent with remote 

 relationships with the Perissodactyla. 



Resemblances to Meniscotherium (p. 355) are seen in the general form of 

 the skull, large orbits, breadth across the orbits, long humerus and femur 

 and largely serial carpus (p. 447). The centrale is likewise still separate, 

 the proximal row of carpals relatively small and the trapezoid large. The 

 magnum in Hi/ra.r, however, is very broad and quadrate. The metacarpals 



