OSTEOLOGY OF THE ARMORED DINOSAURIA. 



73 



The following detailed description of these bones is based upon the foot of 

 an adult specimen of Stegosaurus sulcatus, No. 4937, which is in a beautiful state of 

 preservation : 



Metacarpal I (pi. 21, fig. 2, 1) is the shortest and stoutest element of the series and 

 maj r be distinguished at once by the great breadth of the shaft, being but little con- 

 stricted at the center when viewed from the front. The ends are about evenly ex- 

 panded, the proximal being subtriangular in outline with the rather blunt apex 

 directed inward. This end is roughened and slightly concave, with the outer border 

 beveled off where it 

 meets metacarpal 

 II. The transverse 

 diameter of the dis- 

 tal end exceeds the 

 vertical diameter. 

 This end is convex 

 antero - posteriorly, 

 but concave trans- 

 versely, thus form- 

 ing a broad groove 

 for articulation 

 with the first pha- 

 lanx of this digit. 

 The external sur- 

 face near the upper 

 end is concave an- 

 tero-posteriorly and 

 roughened for the 

 better attachment 

 of the ligaments 

 which bound the 

 metacarpals t o - 

 gether. 



Metacarpal II is 

 longer and more 

 slender than the 



preceding. It is constricted medially, both in its lateral and vertical diameters. 

 From the front the ends appear to be about evenly expanded, but viewed laterally 

 the proximal end is especially produced in a posterior direction, giving the bone 

 a wedge-shaped appearance. The proximal end in outline is that of an equilateral 

 triangle, the surface being roughened and slightly concave antero-posteriorly. (See 

 II, fig. 39.) 



The distal articular surface is broader than deep, being convex antero-pos- 

 teriorly and broadly concave transversely. 



Metacarpal III is the longest one of the five. Its proximal end is about evenly 

 divided between the distal surfaces of the radiale and intermedium in an articulated 

 foot. 



Fig. 38.— Bight foee foot of Stegosaurus sulcatus Marsh. Type. Cat. no. 4397, 

 TJ.S.N.M. i nat. size. 1, Front view, in, Intermedium; r, radiale; ul, coalesced 



INTERMEDIUM, ULNAKE, AND PISIFORM; I, II, III, IV, V, DIGITS ONE TO FIVE. 2, PROXI- 

 MAL VDXW OF CARPAL BONES, SAME FOOT, r, RADIALE; Ul+in+p, COALESCED ULNARE. 

 INTERMEDIUM, AND PISIFORM. 



