CONDYLARTHRA. 399 



of the shaft is triangular, with subequal sides, the posterior flat. The distal 

 extremity is triangulai-, the posterior side longer than the others. This bone 

 is long for the length of the femur and humerus. 



Measurements of tibia without epiphyses. 



Nos. 1 and 3. 



U. 



Total length (derived from two tibipe) 135 



Diameter at middle of shaft J ••^°*"°P°^**^™' ^'^ 



transverse Oil 



Diameter at distal end ^''°t«'-''P°^t''"°'- ^^ 



( transverse 027 



The calcaneum is depressed. The border of the sustentaculum is trun- 

 cate and not acute. The cuboid facet is transverse, wide, diamond- 

 shaped, with opposite angles, the external angle supplemented by a promi- 

 nent flattened tuberosity. The inferior surface has a wide external groove. 

 Free process lost. The external inferior cotylus of the astragalus is very 

 little concave, conformably to the form of the calcaneum. The angle at 

 its externo-anterior termination is not produced downwards, as in Phenacodus 

 vortmani and P. primcBVUs ; still less than in Mesonyx ossifragus. The pos- 

 tero-internal angle is produced beyond the trochlea, but not so much as in 

 Oxycena; its connection with the head is by a flat horizontal ridge. The 

 head is extended laterally in both directions, so as to be wider than the 

 neck. The median inferior or sustentacular facet is separated by deep 

 grooves from the other facets, but is connected with the inferior recurvature 

 of the head. The longitudinal median groove terminates posteriorly in a 

 deep foramen penetrating upwards, and issuing in a posterior notch of the 

 trochlear surface. This foramen is caused by the closing of the usual ten- 

 dinous notch, and is also seen in the genus Bathmodon. The trochlea is 

 strongly convex anteroposteriorly, though nearly flat transversely. There 

 is a depressed fossa beneath its antero-external angle. 



As already remarked, this astragalus resembles somewhat that of Oxy- 

 CPMa. It is preserved in three or four individuals. The navicular is rather 

 shallow, and is wider transversely than anteroposteriorly. Its median facet 

 is the largest, and rises highest in front. The cuboid, which is also pre- 

 served in No. 1, has a square anterior face. Its proximal face is convex 

 anteroposteriorly, and the distal face is concave anteroposteriorly to a less 



