90 



BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



doubtless incased in a horny hoof. Marsh, in the restoration of Stegosaurus 

 ungulMus (pi. 32, upper figure), regarded this digit as the second, and on that 

 account it has been given three phalanges. 



The proximal phalanx of digit II (fig. 52) may be recognized at once when 

 viewed from above on account of its bilateral symmetry. In this aspect the proxi- 

 mal phalanges of digits I and III are wedge-shaped, with the least antero-posterior 

 diameter away from the center of the foot. 



The first phalanx of digit II (fig. 52) had a small flattened discoidal element 

 attached by matrix to its distal end. This element either represents a rudimentary 

 second phalanx of this toe or a sesamoid bone. I am inclined to believe it to be 

 the latter. A similar element was found with the disarticulated foot bearing the 



number 7415. These probably represent 

 phalangial sesamoids such as Hatcher ' 

 found in the manus of Brontosaurus. 



Nothing is known of the positive 

 arrangement of the other phalangials or 

 unguals, and we must await the discov- 

 ery of more complete material for the 

 determination of the digital formula. 



The pes, as in the manus, is digiti- 

 grade. The roughened articular ends of 

 the metatarsals and phalanges indicate the presence of thick pads of cartilage 

 between the joints. 



That the foot was well arched is shown by the wedge-like proximal end of 

 metatarsal II and the oblique proximal phalanges of digits I and III. 



The ungual of digit I if articulated would turn obliquely inward toward the 

 median line of the body. Other unassociated unguals show the ends to be obliquely 

 truncated toward the mesial line, as the one shown in digit III (fig. 52) of No. 

 4280. There are one or two others which are more symmetrical, and probably 

 represent the terminal phalanx of the median toe (Mt. II). With the associated 

 hind-foot bones of No. 4936 there were two disarticulated . unguals present, but 

 whether digit III bears a flattened claw remains to be determined. 



The general character of the bones of the hind foot suggests that the feet of 

 Stegosaurus were much like those of a large tortoise, club-like, with the toes turned 



well downward. 



Measurements of the elements of the pes. 

 METATARSALS. 



Fiij. 54.— Terminal phalanx of Stegosaurus sp. i hat. 

 size, o, Front view; b, side view; c, posterior view. 

 After Marsh. 





No. 4280. 



I 



II 



III 





mm. 

 76 

 55 

 68 

 50 



mm. 

 H7 



mm. 

 100 

 76 

 76 

 43 











34 





PHALANGES, FIRST ROW. 











33 

 60 



35 

 61 



31 



55 







' Ann. Carnegie Museum, vol. 1, 1902, p. 373, tig. 13, pi. 19. 



