Ea RN 
114 MEMOIRS OF THE CARNEGIE MUSEUM 
Radius and Ulna. — As has been intimated above, the ulna-radius in Dinohyus 
is proportionately longer than in Archxothervwm ingens ; it is also more curved or 
bowed forward ; the olecranon process is more truncate ; and the sulcus for the exten- 
sor tendon is less clearly defined. The humeral articulation of the radius differs 
only in minor details from what is seen in the Princeton specimen. The most 
noticeable of these minor differences are: the relatively narrower articular surface 
external to the intertrochlear groove, and a rugose pit, which interrupts the humeral 
articulation near the posterior margin. The transverse diameter of the shaft of the 
ulna-radius is shortest immediately below the head; from this point it rapidly in- 
creases distally, and the distal extremity has only a slightly greater diameter than 
the shaft of the compound bone. All traces of the suture between the radius and 
ulna are practically lost, except at the proximal and distal ends. The deeply 
channeled external face of the shaft shown in Archxotheriwm ingens is not so notice- 
able in Dinohyus. The ridge which separates the pyramidal and lunar facets is 
more developed, and the ridge separating the latter facet from that for the scaphoid 
is less developed than is the case in the Princeton specimen. In this way the 
peculiar condition found in Archxotheriwm ingens in which the ulna occupies the 
entire proximal face of the pyramidal and also effects a lateral contact with the 
lunar is even more emphasized in Dinohyus hollandi. 'The oblique direction of 
these ridges and the articulating surfaces to receive the carpus are practically nearly 
the same as in the Oligocene genus. Between the radius and ulna on the posterior 
face is a deep pit to accommodate the posterior hook-like process on the proximal end 
of the pyramidal when the manus is flexed backward. ‘This pit is less developed 
in Archxotherwwm. ‘The pisiform facetin Dinohyus as in Archxotheriwm is continuous 
with that of the pyramidal. 
MEASUREMENTS. 
Mm 
Win AeHA CUS realest MOUS ON, systea9 yrs evens eee te reer etic naliiat ces raoh cine eac ae oe se 605 
ist Heid: Ohracius) 60. CiStal CNG, cael. caiticcsssvsedudess os vicacee tien steer ey 475 
by length of olecranon process con ales 
of transyerse diameter of head of radiu nee 05) 
Cy ae a “ shaft immediately below head of radius 76 
greatest transverse diameter of distal end...............0..ccseeeeeee 117 
CS “« antero-posterior diameter of distal end..................... 83 
Tur Manus. 
Scaphoid. —The scaphoid is not present in the manus of the type specimen of 
Dinohyus. Judging, however, from the proximal articulation of the magnum and 
the corresponding articulation of the radius, which are quite broad, it is evident 
