312 Bulletin American Museum of Natural History. [Vol. XVI, 



anteriorly to this the muzzle is broken off on both sides (or is 

 not calcified). A longer diastema precedes the alvcjolusof Pg 

 in the lower jaw, and in front of that, on evidence of other 

 specimens, it is known that there are five small subequal teeth, 

 probably incisiform. 



The antorbital foramen is double, opening above the dia- 

 stema in front of the molar series. There appears to be a 

 small prelachrymal vacuity. The postorbital bar is com- 

 plete. The orbit is surrounded by a thin prominent ring, of 

 which the inferior and anterior parts (jugal and lachrymal) 

 are more prominent, and the superior part (frontal) less 

 prominent than in Hypertragnlus or Leptomeryx. The eye, 

 therefore, faced much more upward than in these genera; it 

 was more prominent and much larger in proportion. The 

 basifacial axis is much more bent down on the basicranial 

 axis than in other Hypertragulidae. The bullae are very large, 

 connate anteriorly, with a long, prominent, enclosed meatus 

 opening behind the origin of the zygoma. The occiput 

 projects much more backward than in Hypertragulus or Lepto- 

 meryx. The paroccipital processes are slender, and are co- 

 ossified with the bullae except just at the tip. 



The lower jaw is slender, its condyle set high up, and the 

 long coronoid process is slightly curved. It does not possess 

 the angular hook seen in certain of the Camelidae. 



The limbs and feet I have described in a previous article. 

 The ulna and radius are coossified, and the distal end of the 

 fibula is coossified with the tibia. The cuboid and navicular 

 were coossified, the median metatarsals distinct though ap- 

 pressed, the laterals thread-like but still complete. 



Hypisodus was much less Tragulus-\\\ie than Hypertragulus 

 or Leptomeryx, and superficially resembled rather the dwarf 

 antelope Madoqua. Its real relationships are more nearly 

 with Hypertragulus than anything else, but it is a remarkably 

 modernized animal for the formation in which it is found. 

 The resemblance to Madoqua is a striking instance of parallel 

 adaptation. 



