60 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



Measurements of ulna of Antrodemus valens. 



mm. 



Greatest length 263 



Greatest diameter of proximal end 90 



Greatest diameter of distal end 55 



Least diameter of shaft 24 



Radius (r.). — The radius is more slender and somewhat shorter than the ulna. 

 The proximal and distal ends are expanded, more especially the former (fig. 43). 

 In cross section the shaft is angularly rounded throughout the greater part of its 

 length. The proximal end is shallowly concave in its greatest diameter. Viewed 

 from above this end is suboval in outline. The distal end is subtriangular in outline, 

 with an oblique surface that looks downward and outward. It 

 ■o articulates exclusively with the radiale of the carpus. The inner 

 surface where the-radius meets the ulna is slightly roughened. 



Measurements of radius of Antrodemus valens. 



mm. 



Greatest length 222 



Greatest diameter of proximal end 56 



Greatest diameter of distal end 40 



Least diameter of shaft 20 



Carpus. — The ossified carpus in Antrodemus consists of at least 

 five elements, with a possibility of there being one more. Three 

 disarticulated elements were found with the bones of the left foot 

 and three with the right, but since there is an element with each 

 foot that is not present in the other, and the ulnare is lacking in 

 both, the presence in the complete .carpus of five ossified carpals 

 is quite conclusively demonstrated. Fortunately two of those 

 pertaining to the right foot (figs. 40 and 45, in. and c 2 ), the 

 intermedium and a carpale, probably c 2 , were found in position, 

 fig. 42.— left ulna of firmly attached to metacarpals I and II, and these give the first 

 definite knowledge we have of the exact manner of their artic- 

 ulation. Without such evidence it would be almost impossible 

 to place them properly. I was also able to determine the proper 

 articulation of the radiale by its position as found in the matrix 

 and also by its close articulation with the grooved surface of the intermedium. 



The radiale is a flattened discoidal element, irregularly oval in outline (fig. 

 44, a) . The upper articular surface is shallowly concave, while the distal surface is 

 angularly convex. This surface in the articulated foot articulates for more than 

 half its area with the intermedium, and slightly, if at all, with the outer anterior 

 corner of metacarpal I. Its greatest transverse diameter is 41 mm.; greatest 

 thickness, 15 mm. 



The intermedium, as shown in figure 44, o, is an irregularly quadrangular 

 bone. Articulated, it rests about equally upon the proximal ends of metacarpals 

 I and II (fig. 45 in. and ra.). The upper surface presents a broadly grooved surface 

 for the radiale, with a projecting spur on the anterior face that continues to the outer 

 border of metacarpal I, so that when viewed from the front it appears to completely 



Antrodemus valens 

 Leidy. Cat. No. 4734, 

 XJ.S.N.M. % NAT. SIZE. 

 POSTERIOR VIEW. 0, 

 OLECRANON PROCESS. 



