THE MAMMAIJA OF THE DEEP RIVER BEDS. 173 



parallel with the straight upper surface of the skull. There is no trace of a lachry- 

 mal pit in front of the orbit. In B. borealis, and doubtless in the present species 

 also, the maxillaries are sharply constricted in front of the premolars. The infra- 

 orbital foramen occupies a slightly less advanced position than in Moschus, opening 

 above the internal between M and pjj, while in the existing genus it is over the mid- 

 dle of pj*. The palate is broad and gently arched from side to side ; between the 

 molars it is of nearly uniform width, but it narrows anteriorly, the two premolar 

 series converging slightly forward. The posterior nares extend to about the middle 

 of n^j and are very long from before backward, in correspondence with the length 

 of the cranium and zygomatic arches. As contrasted with the base of the sknll in 

 Antilocapra, the principal difference to be observed is the elongation of the posterior 

 portion, especially the region between the occipital condyles and paroccipital pro- 

 cesses, which points to a greater development of the cerebellum and medulla oblon- 

 gata and is very usual in the crania of primitive mammals. The orbit is also much 

 lower down and farther forward in the face, its upper border not projecting above the 

 superior contour of the cranium. 



Nothing is known of the mandible in either species, except some uncharacteristic 

 fragments. 



From the foregoing description it will be at once evident that while the skull of 

 Blastomeryx is in many respects more primitive than that of any of the recent Pecora, 

 yet it is manifestly of that type and, in some details, such as the character of the 

 occiput and the wing-like processes from the bases of the horns, the genus is special- 

 ized in a way peculiar to itself and which renders it somewhat doubtful whether 

 any existing form is to be derived from it. * 



Measurements. 



BLASTOMBRYX ANTILOPINUS. ANTILOCAPRA AMEUICANA. 

 M. M. 



Width of occiput at foramen magnum 078 .079 



Distance lrom crest of inion to middle of horn 104 .085 



Antero-posterior diameter of horn base 036 .041 



Transverse diameter of horn base 046 .024 



Depth of face at m. 3 . 067 .070 



Distance from foramen magnum to postglenoid process 051 .045 



Distance from postglenoid process to m. 3 073 .069 



Width of palate at m. 3 036 .052 



The vertebral column is represented by the second, third and fourth cervical 

 vertebrae. The axis is completely modernized in character and differs only in details 

 from that of Cervus or Antilocapra. The centrum is broad anteriorly, where it 



