LAGOMOEPHA. 871 



dric, consisting of but one column. The first inferior molar consists of two 

 cylinders broadly united, as in the corresponding tooth of Palceolagus. As 

 compared with Panolax Cope,^ which is only known from superior molar 

 teeth, this genus may be at once recognized by the simplicity of the last 

 tooth. In Panolax it consists of two columns. 



Dr. Leidy's descriptions and figures, which are available for the defini- 

 tion of this genus, I'elate exclusively to the dentition. Characters drawn 

 from the skeleton generally have been derived from my material and are now 

 given. 



The nasal bones are wide, and the suture which separates them both 

 from the frontal is concave forwards. The median frontal suture is persist- 

 ent. The ascending portion of the premaxillary, which attains the frontal, 

 is very narrow. The superior half of the facial plate of the maxillary bone 

 is sharply rugose with reticulate ridges, but whether perforate or not I can- 

 not certainly determine. The foramen infraorhitale is small and round, and 

 issues below the reticulate portion of the maxillary. The otic bulla is com- 

 pressed globular, with very thin walls. The meatus is large and has prom- 

 inent lips, which open upwards. The mastoid is coossified with the bulla, 

 and extends with a dense surface from behind to above and in front of 

 the meatus. The incisive foramina are veiy large, enter the maxillary 

 bones deeply, and are confluent posteriorly. The palate may be said to 

 extend to the last molar, but there is a deep though narrow median poste- 

 rior emargination. 



The distal extremity of the humerus is not so extended transversely as 

 in Iscliyromys, and exhibits a moderate epicondyle. The inner flange of the 

 condyles is well developed, and on the posterior face it is supplemented by 

 a flange of the external edge of the condyles, which is as prominent or even 

 more so, forming an intertrochlear crest. The arterial canal is inclosed by 

 a slender bridge, and opens on the inner side above, and anteriorly below. 

 In an ulna supposed to belong to this genus the coronoid process is elevated. 

 The radial facet forms a narrow transverse plane, nearly divided by a wide 

 anterior emargination. The shaft is compressed vertico-obliquely. A radius 



'Report Lieut. G. M. Wheeler, 4to, IV, p. 296. 



