74 



BULLETIN ll'O, UNITED STATES NATIONAL MUSEUM. 



portion of metatarsal I. On the posterior side, at a point about midway, a flat- 

 tened rugose area appears to represent the point of attachment for the distal por- 

 tion of metatarsal I. 



The distal articular surface is rounded and produced well up in front and back. 

 Posteriorly, this end is deeply excavated by a wide groove that passes upward from 

 the articular surface. The lateral pits of this end are well defined, the one on the 

 side nearest metatarsal III being the deepest. 



Metatarsal III is the longest bone of the foot. Its proximal end is compressed 

 transversally, but is long antero-posteriorly, widest in front, with a plane lateral 

 surface for union with metatarsal I. These two bones are in the closest apposition 

 throughout the upper three-fourths of their length. The lower fourth of metatarsal 

 III when viewed from the front swings outward. The distal end is pulley shaped, 

 the rounded articular surface extending well up on the front and back. The pits 



for the attachment of 

 the lateral ligaments are 

 of large size and of 

 moderate depth. The 

 front of the shaft is 

 flattened on the back 

 and external side quite 

 evenly rounded but on 

 the internal side bev- 

 eled off from the heavy 

 obtuse longitudinal edge 

 along the antero-inter- 

 nal border, which over- 

 laps to some extent the 

 shaft of metatarsal II 



Fig. 51.— Proximal ends of the articulated left metatarsals of .\ntrodemus when these bouCS are 



valensleidy. No. S423, u.s.n.m. * N.iT. size. II, HI, and IV metatarsals two, nrt^jp^ijatpfi Theuuuer 



THREE, AXD four RESPECTIVELY. " ^^ . 



end of metatarsal I\ is 

 roughly surtriangular in outline, the apex being directed inward and backward, the 

 antero-internal side of this end being widely excavated for the articulation of an 

 outward projection from the head of metatarsal III. This bone, when viewed from 

 the front, is bowed from end to end, which tlrrows the lower half of this bone out- 

 ward from the median or third metatarsal. The distal articular end is triangular in 

 outline, the apex of the triangle extending well up on the front of the bone. The 

 posterior face is bisected by a Made shallow groove. The lateral pit is wanting on 

 the external side, whfle the internal one is not well defined. In section, at the 

 center, this bone is triangular. 



Phalanges. — The digits of Antrodemus have the usual number of phalanges, 

 that is, two, three, four, and five, as in nearly all other bipedal dinosaurs. 



The proximal phalanges of each digit are the most elongate of the digital 

 series. Those of digits II and III are the longest and most robust, being subequal 

 in length, though the former is compressed transversally, the latter depressed 

 vertically. All proximal phalanges articulate with their respective metatarsals 



