100 THE ROYAL SOCIETY OF CANADA 



However, there is no doubt as to the phalangial formula, which is, 

 digit I = 2, II = 3, III =3. So far as the writer is aware this is the first 

 articulated forefoot of an armored dinosaur to be described. 



The metacarpals resemble one another in general shape and 

 proportions. They are not nearly so robust as those of Stegosaurus 

 figured by Gilmore, nor are their extremities so much expanded. The 

 transverse expansion at the distal end is less than half the length. 

 They are only slightly constricted medially. 



Metacarpal I is shorter and less expanded distally than either 

 of the others. The proximal end, which is flat and slightly rugose, is 

 subtriangular in outline, with the gently rounded apex of the triangle 

 pointing inward (toward the opposite foot). The broad base of the 

 triangle is applied to the broad inner face of the proximal end of meta- 

 carpal II. The distal end is convex antero-posteriorly and flat 

 transversely. 



The proximal end of metacarpal II is rugose, slightly convex 

 and subquadrate in outline. The anterior face is longer than the 

 other three, which are about equal in length. The sides of the 

 proximal end are broad, forming a surface for contact with the meta- 

 carpal on either side. The distal end is convex antero-posteriorly and 

 flat transversely. 



Metacarpal III does not differ greatly from metacarpal II, 

 except that the external surface of the proximal end is shorter than 

 the other three sides, and on the inner side of the proximal end is a 

 large rugose area, evidently for the attachment of ligaments which 

 bound the foot together. 



The lengths of the three digits are approximately equal. The 

 proximal phalanx of digit I is moderately long and narrow as com- 

 pared with the other proximal phalanges. The proximal end is flat 

 and the distal end is slightly convex antero-posteriorly and flat 

 transversely. 



The proximal phalanx of digit II is short and broad, the length 

 being but half the breadth. The proximal end is concave and the 

 distal end convex antero-posteriorly. The superior and inferior 

 surfaces are slightly concave and pitted with small foramina. 



The proximal phalanx of digit III is much the same as that of 

 digit II both in size and shape. The second phalanges of digits II 

 and III differ only in being shorter. 



The ungualar phalanx of digit I is moderately long and slender 

 and tapers from its proximal end, which is broadest, to a rounded apex. 

 The unguals are all flattened hoof-like bones which in life were doubt- 

 less incased in a horny nail. 



