OSTEOLOGY OF THE ARMOKED DINOSAURIA.. 



71 



Both pertain to small, partly grown animals. These supplementary specimens show 

 very clearly the entire Stegosaums carpus, as may be seen by comparing figures 

 36 and 37. 



Professor Mareh recognized three elements in the pi-oximal segment of the car- 

 pus and so indicated it in his restoration of 

 the skeleton.' Yet later in defining the genus 

 Diracodon^ he observes that " in the fore foot 

 the intermedium and ulnar bones separate, 

 while in Stegosaums these carpals are firmly 

 coossified," evidently overlooking the fact 

 that in plates 48 and 52 of the same article, 

 feet of the genus Stegosaums are shown with 

 these elements separate. 



Radiale (jr.). — The radiale is much the 

 largest bone (see figs. 37 and 38, r) of the car- 

 pus and is opposed distaUy by metacarpals 

 I, II, and partly by III. Proximally it artic- 

 ulates exclusively with the radius. It is a 

 block-like bone, wider than long, with upper 

 and lower articulating surf aces roughened, the 

 former being flat, the latter rather angxilarly 

 convex transverselj'. The sides are vertical 

 with the exception of the posterior, which has 

 on its outer posteiior half a rounded depres- 

 sion of some depth. The principal dimen- 

 sions of the radiale of an adult and a young 

 specimen are given below : 



Measwements of radiale. 



Fig. 37.— Caepds (lacking pisifoem) and portion of 



EIGHT FOEE FOOT OF STEGOSAUETJS SP. JUVENILE. 



Cat. no. 7401, U.S.N.M. J nat. size. A, Front and » 

 B, TOP VIEWS, in. Intermedium; r, radiale; ul, 

 ulnaee; I, II, III, metacarpals one, two, and 

 three. 



Greatest transverse diameter 



Greatest antero-posterior diameter 

 Greatest vertical diameter 



Juvenile, 

 No. 7401. 



Adult, No. 

 4937. 



mm. 



mm. 



72 



no 



62 



103 



SO 



70 



Intermedium {in.). — The intermedium will be described from the young speci- 

 men bearing catalogue No. 7401. Viewed from above {in., fig. 37, B) this bone 

 is triangular in outline, the front forming the longest side. The anterior face is 

 shaUowly concave doi-so-ventrally, with an arterial foramen notching the external 

 border. In adult animals all traces of this notch are obliterated. 



The upper rugose surface is regularly convex transversely. It articulates with 

 the radiale and ulnare by straight, vertical ends. In an articulated foot it is sup- 

 ported in part by both metacarpals III and IV. Above it meets about equally the 

 distal ends of the radius and ulna. 



I Amer. .Toum. Sci., vol. 21, 1881, pt. 4, p. 170. 



> Dinosaurs of North America, 



