90 DINOCERATA. 



the middle of the bone. Here it unites witli the oblique, and well 

 developed, deltoid ridge, then descends rapidl}-, and ends in a roughened 

 surface just above, and inside of, the coronoid fossa. The deltoid ridge is 

 strong, oblique, and elongated, as is well shown in the back view of the 

 humerus, Plate XXVIIl, figure 3. It does not, however, rise into a 

 hook-like process, as in the rhinoceros. The bicipital groove is single, 

 as in the elephant, and presents no median ridge. The lesser tuberosity 

 is small and low, and wholly below the head, which is broad and 

 extensive, covering much the greater part of the superior aspect of the 

 bone, and extending- forward to the bottom of the bici^aital groove. 



The shaft of the humerus is most constricted at a point nearly tliree- 

 fourths of the way toward the distal end, and here is distinctly triangular 

 in section, one of the angles projecting forward, as seen in Plate XXVIIl, 

 figure 1. Above and below this point, the sliaft expands, and is more 

 flattened, especially distally. Here it is excavated in front, as usual, by a 

 large rounded and deep coronoid fossa, ^jhiced well toward the outer, or 

 radial, side, as shown in Plate XXVIIl, figure 1. The posterior surface 

 is hollowed out, medially, by a comparatively shallow anconeal fossa, as 

 shown in figure 3 of the same Plate. The coronoid fossa in some 

 specimens (number 1224) is even deeper than the anconeal, and is always 

 distinct and rounded. The anconeal fossa is also rounded in general 

 outline, median in position, and is carried but little below the trochlear 

 articular face. 



The posterior surface of the humerus is bounded, on the inner side, 

 by a ridge running almost the entire length of the shaft. This ridge 

 commences above, near the posterior part of the lesser tuberosity, and the 

 postero-intemal angle of the head, and runs nearly straight down the sliai't 

 of the humerus, terminating in an expanded and tubercular tract, on the 

 inner condyle. On this ridge, and about the middle of the shaft, nearly 

 opposite the strongest part of the deltoid ridge, is another roughened area, 

 often, as in the specimen figured (Plate XXVIIl, figures 1, 2 and 3), 

 rising into a distinct trochanter-like eminence, apparently for the insertion 

 of the latissimus dorsi muscle. At the lower end of the humerus, this ridge 



