1884.1 553 [Cope. 



only be guessed. Perhaps it supported an inflatable bladder like that of 

 the crested seal, or a swollen muzzle like that of the saiga antelope. 



Cyclopidius emydimis, sp. nov. 



This species is represented in my collection by a nearly perfect cra- 

 nium. It indicates an animal of about the same size as the G. simus. The 

 differences between the two species may be enumerated in advance of 

 the detailed description. Firstly, the external vertical ridges or crests of 

 the true molars are directed obliquely forwards so as to overlap the ex- 

 ternal wall of the anterior crescent much more extensively than in G. 

 simus. (2) The crowns of the true molars have a relatively greater trans- 

 verse diameter. (3) There is a peculiar process at the external base of the 

 otic bulla, between the paroccipital and postglenoid processes, which may 

 be called the subtympanic process. (4) There is no median occipital 

 keel. (5) The maxillary bone is prolonged posterior to the last superior 

 molar, which it is not in G. simus. (6) The oblique orbitosphenoid ridge 

 is wanting. (7) The otic bullae are shorter and wider in their form. This 

 character will require confirmation by examination of many individuals. 



The skull is singularly depressed and expanded laterally, so as to pre- 

 sent an outline not unlike that of some river turtles. The orbits are in 

 the anterior half, and look forwards and upwards, as well as outwards. 

 The muzzle is short, so that its lateral borders approximate rapidly to a 

 narrow truncate extremity. The maxillary borders do not contract quite 

 so abruptly, and are visible outside of the canthus rostralis, when the 

 skull is viewed from above. The brain-case is depressed, and is expanded 

 posteriorly, and narrowed at the anterior line of the zygomatic foramina. 

 The posterior temporal ridges are much expanded, forming a wide rim 

 round the brain-case posteriorly, which is continued into the squamosal 

 processes of the zygoma on each side. The anterior temporal ridges ap- 

 proach each other very gradually on the middle line, and only reach the 

 union into a sagittal crest a centimeter posterior to the frontoparietal su- 

 ture. The edge of the crest is truncate, and it is not bifurcate posteriorly, 

 as in most Oreodontidae. 



The occiput is broad and low, and differs in character from that of most 

 other members of the family. Its posterior face is flat, only interrupted 

 by a fossa on each side, just within the posterior edge of the meatus audi- 

 torius externus. This edge is continued downwards into the external bor- 

 der of a distinct mastoid process, which is also the external border of the 

 occiput, deflected a little forwards. The paroccipital process is flat at the 

 base, and is applied to the external half of the otic bulla. Its free extrem- 

 ity is subround. The mastoid process forms a prominent ala of its exter- 

 nal side, having a transverse width equal to that of the base of the par- 

 occipital. Its inferior edge is truncate obliquely outwards and downwards 

 to a subacute angle. The occipital condyles are relatively small. 



The external meatus of the ear looks outwards and backwards at an 

 angle of 45° to the middle line. The prominent edge of the mastoid pro- 



