J 877.] ^1 [Cape. 



Measurements. M. 



Diameter of canine tooth (transverse) 004 



Width of cranium between first premolars 016 



" " " last molars 030 



The cranium of this species is about the size of that of a large domestic 

 cat. 



Cycloptdius simus. Gen. et. sp. nov. 



Oliar. gen. Dental formula I. § ; C. \ ; Pm. f- ; M. f . The superior 

 canine is small and is separated from the first premolar by a very short 

 diastema. First premolar simple, trenchant ; second premolar two rooted, 

 with one principal cutting edge ; third with an external crescent and a 

 rudimental internal one, not united in front. Fourth premolar with the 

 inner and outer crescents only, and these well developed. Last true molar 

 without heel. Inferior canine with much wider crown than the incisors 

 with which it is in close association. First premolar canine-like, but not 

 very large ; second premolar simple. Third and fourth premolar with the 

 anterior portions trenchant, the posterior with wide or double columns. 

 Last true molar with large fifth crescent or column. True molars of both 

 jaws prismatic. Symphysis mandibuli coossified. 



Frontal bones much abbreviated in front by a large upwards- looking 

 fossa on each side, which are separated by the very narrow and short nasal 

 bones. There are' lachrymal fossae and a huge foramen in front of them, 

 which communicate with the maxillary sinus. There is a prominent trans- 

 verse supraoccipital crest, and the otic bullae are greatly inflated. 



This genus is related to Leptauchenia, Leidy, but differs in having but 

 two lower incisors below. That genus belongs to a lower horizon, the mi- 

 ocene of White River, while the present form is its successor in the upper 

 Miocene or Loup Fork beds. The remarkable character of the vacuities in 

 the superior region of the front part of the cranium, reminds one of the 

 existing genus Smga. Dr. Leidy partially described a similar structure in 

 Leptauchenia. In this genus what are clearly nasal bones in Cyclopidius, 

 he terms front.jls, probably by error. 



Char. Specif. This animal is rather larger than either of those above 

 described, and is represented in my collection by one nearly complete cra- 

 nium, one entire left maxillary bone, and the under jaws of five, and prob- 

 ably of several other individuals. 



The skull is wide and abbreviated in front. The maxillary bones are 

 everted on each side of the external nares. The malar bone is very wide 

 or deep, and sends upwards a strong postorbital process, which is broken 

 off in part, but which probably completed the orbit. The superior facial 

 fossa? reach backwards nearly as far as the middle of the orbit. They are 

 longitudinal narrow ovals, open in front. The projecting supraorbital por- 

 tions of the frontal bone with the nasals have a tripodal form. The lach - 

 rymal fossa looks outwards, upwards and forwards, and the large maxillary 

 foramen outwards. The infraorbital foramen is double, and issues above 

 the contiguous portions of the third and fourth premolars. 



