210 
PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
the blade is much the same in the two genera, but in Adinothevium the 
coraco-scapular notch is shallower and less distinct and the coracoid 
border has a more regularly convex curvature, passing without angula- 
tion into the suprascapular border. The spine arises farther below the 
suprascapular border and rises to its full height more abruptly. The 
two metacromial processes are of quite different shape and relative size 
from those of the larger animal ; the proximal one is smaller and of 
more triangular shape, while the distal one is much longer and narrower 
and has a rounded border at the free end, instead of the straight border 
seen in Nesodon. In all of the available specimens the acromion proper 
is broken away, but, from the thinness of the fractured bone, it is very 
probable that this process was decidedly shorter than in Nesodon and 
may have been almost absent. The coracoid also is very small and 
much more reduced than in the last-named genus. 
The humerus (PI. XXVII, fig. 4) differs little, save in size, from that 
of Nesodon. The external tuberosity is a high and very broad ridge, 
which extends across nearly the whole proximal end, concealing the head 
in front-view ; the free proximal border is more horizontal than in Neso- 
don. The internal tuberosity is very small and the broad bicipital groove 
is divided into two parts by a very inconspicuous bicipital tubercle, which 
is in hardly more than an incipient stage. The deltoid ridge is more prom- 
inent and ends more abruptly below than in Nesodon. The distal end 
of the humerus differs in a number of particulars from that of the latter 
genus ; the supinator ridge is longer and more prominent, but the epi- 
condyles, especially the external one, are much less so ; the trochlea is 
relatively narrower and has a more prominent internal flange for the ulna 
and a more convex facet for the head of the radius ; the supratrochlear 
fossa is shallow, but the anconeal fossa is very deep and a perforation 
connects the two. 
The fore-arm bones are almost exact replicas, on a smaller scale, of 
those of Nesodon , with hardly any differences that can be expressed in a 
description. The ulna (PI. XXVII, figs. 10, 11) has a very prominent 
and stout olecranon, which, however, is relatively somewhat shorter than 
in the last named genus. The sigmoid notch is almost identical in form 
in the two genera, but in Adinothevium the external border of the prox- 
imal portion is not flared upward so strongly, while the distal portion 
presents more anteriorly and less proximally. The shaft, which is rela- 
