THE MAMMALIA OF THE UIXTA FORMATIOX. 527 



Tii]}lo]ni.-^. The fimgs of three subeqnal incisors and a modiuin sized canine are pre- 

 served, behind which is an extended diastema, followed in the left jaw by the minute 

 alveolus of pm/ which may have been retained in sila at a less mature age. In the 

 right jaw no trace of this alveolus can be seen. If this premolar is found to be in- 

 variably missing, this may be given as the generic distinotion of Prollnimcodon. 

 The second premolar is rather small, the third and fourth are submolarifoi'm. The 

 three molars are nearly equal in size with the ordinai-y lophiodont pattern, the ante- 

 rior crest is well incurved in the worn condition of the crown. The mandible is stout 

 and well rounded, contracting greatly opposite the diastema. The measurements 

 indicate a heavier jaw and laiger animal than the type of T. cubitalis. The last 

 molar has no ti-ace of the third lobe, but there is a considerable space between it and 

 the ascent of the coronoid process. 



The third specimen (10,397) is of unusual interest, since it contains, associated 

 with a few teeth, many portions of the skeleton and the complete tarsus and carpus. 



The Fore and Hind Limhs. 



The fore limb of T. cubitalis has been fully described by Cope, op. ciL, p. 081. 

 It is remarkable for the unusual elongation of the fore arm and of the manus. The 

 head of the humerus is laterally compressed, with marked fore and aft extent; 

 the distal trochlea is unusually deep and extensive, indicating great play at the elbow 

 joint. The distal portion of the scapula has a very long neck, and the spine 

 rises very gradually ; the scapula was probably high and narrow. The pi'oximal 

 facet of the radius is very deep antero-posterioily. The ulna is remarkable for the 

 great extension of its olccraTion ; distally it is apparently more reduced than ui T. 

 cubitalis. 



The extremities of the bones of the hind Ivnb are mostly preserved, and indicate 

 that the proportions were long and slender. The femur has a long patellar facet and 

 a deep intercondylar pit. The tibia has a narrow but prominent cnemial crest and 

 double spine ; the distal face has a deeply excavated astragalar trochlea which is 

 decidedly oblique. The iibida has a fairly stout distal extremity, and is throughout 

 entirely distinct from the tibia. 



The carpus (Fig. G). The scaphoid is very stout with a deep radial facet ; 

 inferiorly it presents a minute facet for the trapi'ziiim, an oblique trapezoid facet, sub- 

 equal with the slightly larger and horizontal magnum facet. The lunar has a 

 nearly horizontal unciform facet and vertical ental facet which rests partly against 

 the scaphoid and has a slight magnum contact. The c u n e i for m is very thin, and 

 has a narrow ulna facet extending into that Ibr the pisiform. The trapezium was 



