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PROCEEDINGS OF THE NATIONAL MUSEVM. 



VOL. 49. 



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 articulates exclusively with the radiale of the carpus. The inner 

 surface where the radius meets the ulna is slightly roughened. 



Measurements of radius. 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 Allosaurus consists of at least five 

 elements, with a possibihty of there being one more. Three disar- 

 ticulated 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 

 (fig. 7, in and c^), the intermedium and a carpale, probably Cg, were 



found in position, firmly attached to 

 metacarpals I and II, and these give 

 the first definite knowledge we have 

 of the exact manner of their articu- 

 lation. 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. 6a). 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 sHghtly if at all with the inner posterior corner 

 of mtc. I. Its greatest transverse diameter is 41 mm.; greatest 

 thickness, 15 mm. 



The intermedium as shown in figure 66, is an irregularly quad- 

 rangular bone. Articulated it rests about equally upon the proximal 

 ends of mtcs. I and II (fig. 2, in and ra). The upper surface presents 

 a broadly grooved surface for the radiale (fig. 7), with a projecting 

 spur on the anterior face that continues to the outer border of mtc. I, 

 so that when viewed from the front it appears to completely cover 

 the metacarpal. On the posterior external side a somewhat similar 

 projection overlaps a beveled surface on the outer proximal end of 



Fig. 6.— Carpal bones of allosaueus fka- 

 GiLis Marsh. Cat. No. 4734, U.S.N. M. Jnat. 

 SIZE. Viewed distally. a, eadlale of the 

 RIGHT fore foot ; 6, intermedium of the 



LEFT FORE FOOT; //, SURFACE ARTICULATING 

 WITH METACARPAL II, /, SURFACE ARTICU- 

 LATING WITH METACARPAL I. 



