62 Annals of the Carnegie Museum. 



those of Ardomys {MarmotaY^ but with the inner keel of the astragalar 

 trochlea heavier. The peroneal tubercle of the calcaneum is located 

 well up, as in Marmota and Sciurns. The cuboid is possibly somewhat 

 broader and lower than in P. robnstiis, while the entocuneiform appears 

 to be higher, and upon comparison totally unlike that given on p. 49 

 of Dr. Matthew's paper. In the latter species this bone apparently 

 does not extend as high as the proximal face of the navicular. Added 

 to this, regard must be paid to Matthew's statement on the same page, 

 that the presence of the pre-hallux is not demonstrated in P. robustus.^ 

 In the present specimen, the entocuneiform extends high above the 

 navicular and terminates in a broadly rounded tubercle considerably 

 greater in its diameters when compared with those of the marmot or 

 Sciurns. From this round and rather smooth head I would judge that 

 there was present a plantar sesamoid or pre-hallux in the case of this 

 individual. The proportional size and shape of the metatarsals seem 

 to agree quite well with those of the marmot, while the distal articula- 

 tion is distinctly more hemispherical, in this respect disagreeing with 

 those of P. rohustus illustrated by Matthew. The phalanges are 

 also broader and possibly more depressed than in P. rohustus. 



Measurements. 



Length from top of astragalus to distal end of Mt. Ill 60 mm. 



Length from top of astragalus to proximal end of Mt. Ill 30 



Transverse diameter of tarsus, approximately 23 



Greatest length of astragalus 20 



Transverse diameter of trochlea 12 



Length of Mt. I 20 



Length of Mt. II 29 



Length of Mt. Ill 31 



" See Palmer "North American Fauna," U. S. Dept. Agri. Bull. No. 23, p. 400. 



2" In a letter from Mr. Gidley dated May 22, 1916, he states: "In the foot of P. 

 robustus figured by Matthew, the top of the entocuneiform is broken off. But in 

 the other specimen figured, which he referred to P. delicatus, this bone is complete, 

 and shows the same backwardly directed ascending process on its proximal end as 

 in your specimen. No. 3376. It is a little more strongly developed, however, in the 

 latter. This development of the entocuneiform is usual in rodents having penta- 

 dactyl feet with unreduced digits (Compare squirrels and Aplodontia). . . . 

 Although the distal facet of the astragalus is broken off in your specimen, there 

 seems to be evidence of its having had a pre-hallux. Matthew is certainly mistaken 

 in his observation regarding this element in their specimen of P. robustus. The 

 astragalar facet and the navicular both show evidence of a pre-hallux having been 

 present." 



