No. 2. J COPE ON MIOCENE EODENTIA. 365 



The Immenis is rather slender, and the deltoid crest does not exhibit 

 the prominence so usual in the Muridcc. It is most prominent on the 

 antero-external aspect of the shaft near its middle ; an external as well 

 as an anterior ridge diverges from it upwards. The condyles have no 

 intertrochlear ridge, and the external trochlea is not more extended 

 transversely than the internal, measuring from the fundus of the groove. 

 There is a moderate internal epicondyle, and the arterial foramen is 

 distal, and oi)ens anteriorly below and on the external face above. The 

 bridge is slender and moderately oblique. The external border is acute 

 and twisted. 



The ischium is characterized, like that of other Sciuridce, by the 

 presence of a spine or process which is wanting in ISTorth American 

 JlhiHdce, but is present in Perognathus. The bone is rather short, the 

 tuberosity is but little enlarged, and the pubic process not very wide. 

 The proximal end of a femur may belong to Eumys elegans, but is too 

 small according to usual data. The great trochanter is elevated as 

 high as the head, from which a deep notch separates it; its posterior or 

 fossa is pronounced. The little trochanter is very prominent, projecting 

 at right angles to the shaft. The shaft is broken, so that the presence 

 of a third trochanter cannot be ascertained. The distal end of the 

 femur is characterized by a patellar groove of moderate width, with 

 fairly elevated ridges which are continued well posteriorly on the 

 shaft, but not further than in existing Sciuridce, and not so far as in 

 Fakvolagus. The distal extremity of the tibia displays characters of 

 the Sciuridce as distinguished from those of MuridcE and Leporidce. The 

 fibula is of course distinct, and the external trochlear groove opens 

 from its fnndus outwards. The internal groove is narrower and is 

 bounded internally by a vertical malleolus, which has no distal articu- 

 lar facets, and which does not project, but is flat on the inner side. 

 The greater iDart of the posterior face is occupied by the bones of the 

 wide groove for the tendon of the flexor longus polUcis muscle. Its 

 inferior edge is produced downwards as far as the malleolus, from which 

 is is separated by the deep groove for the tibialis posticus and flexor 

 longus digitorum muscles. This groove is marked on the inner side of 

 the distal portion of the shaft, its anterior border being especially weU 

 defined. 



Two species of this genus are certainly known. They belong to the. 

 White Elver horizon of Colorado. They differ, so far as known, chiefly 

 in size, and in the proportions of the inferior premolar tooth. 



MENISCOMY^ Cope. 



Paleontological Bulletin No. 30, p. 5, Dec. 3, 1878 ; Proceediugs American Philosoph- 

 ical Society, 1878 (1879), p. 67. 



The characters of this genus are derived from the dentition of both 

 jaws, and from portions of the cranium which are preserved. The 

 molars are rooted, and number f or | §^. Those of the superior series 



