406 G. R. Wieland — Archelon ischyros. 



parity in size, is in the minor development of the small 

 trochanter, which is little more than a rngosity for ligamental 

 attachment. It is 17^"" long and 11 wide, and subovoid in 

 shape with the greatest expansion above, and slight concavity 

 on its inner and obliquely upward facing expanse. The gen- 

 eral aspect is, however, moderately convex, owing to a heavy, 

 oblong ridge which crosses obliquely from the upper, outer 

 portion to the lower, inner edge. In gigas the small trochan- 

 ter is prominent, being set on an ala 8^°^ in length and nearly 

 2'^^"^ in height. The bases, therefore, bear out the general 

 proportions of the two bones. 



The bicipital groove is a wide and heavy channel, much 

 more marked on the inner side, where it expands into a sub- 

 ovoid concavity whose greatest depth is about 2*^°". The inner 

 surface of the fan-like distal end is longitudinally concave, 

 both anteriorly and posteriorly, while the central portion forms 

 a massive, expanding convexity, terminating in the articular 

 face. 



The outer surface is very flatly convex, and conspicuous for 

 a deep groove S*'"' wide and 4*^°^ deep, as it ends in the articu- 

 lar surface. The posterior border of this groove lies in the 

 exact distal center. The distal articular surface shows no very 

 distinct divisions. It is both laterally and anteroposteriorly 

 convex, and mostly posterior to the great distal groove, and 

 the centrally place enlargement of the inner aspect which 

 receives it. The surface of the humerus is covered with min- 

 ute striae, with larger striations, about l"""" wide and several 

 centimeters long, at short intervals. (Of the humeri, the left 

 is entire, but only the distal third of the right was procured.) 



Measurements of Humerus^ 



Meters. 



Greatest length '65 



Length from head _ '58 



Width at head, antero-posterior -28 



Greatest circumference about base of the head. '50 



Circumference of great trochanter -45 



Least width of shaft _ '17 



Least thickness of shaft '09 



Circumference at least width of the shaft -435 



Greatest distal width . _ '34 



TJlna. — The ulna is short and comparatively massive, but 

 lacks the immense proportions of the humerus. The proximal 

 articular surface is large and quite regular in outline, flat from 

 side to side, and moderately convex antero-posteriorly (see 

 dimensions). Anteriorly the proximal end bears a broad and 

 shallow groove, disappearing at the middle of the shaft and 



