136 DR. H. F. STANDING ON SUBFOSSIL 



the outer surface of the bone. The outer edge is continued down to a prominent 

 tubercle (the " middle thecal tubercle " of human anatomy), but in the bone under 

 consideration it is a broad prominent ridge of about 1 inch in length. The two 

 facets seen on the inferior surface of the radius of Megaladapis are here represented 

 by a single concavity of roughly semicircular outline which extends across the end of 

 the bone from the styloid process to the lower edge of the sinus lunatus. 



The Ulna. 



The two ulnse referred to in the previous section will alone be here described. That 

 figured (No. 1 in Table 21) is the ulna oi Megakulapis (text-fig. 36). Its carpal end is 

 imperfect, but its length estimated from its corresponding radius is approximately 

 290 mm. This bone is slender and much curved, its curvature being slightly less than 

 that of the radius. The proximal end is remarkable for its curious general resemblance 

 to that of the Hotninidse. The greater sigmoid cavity is broad and deep. It is less 

 distinctly divided into two lateral halves than in the human ulna. The coronoid 

 process is high and somewhat oblique in direction and internal in position. The 

 olecranon does not extend backwards beyond the sigmoid cavity in a long process as 

 in the majority of the Lemuroids and Monkeys, but its condition closely resembles that 

 of Man. Its lower surface is rounded off, being convex both transversely and longitu- 

 dinally. The shaft of the bone has a somewhat rounded anterior ridge, the surface 

 external to this ridge being concave, while the internal one is convex. The posterior 

 surface is broad and fiat. The external boundary of this under surface is a long 

 sweeping curve which can be traced from the lesser sigmoid cavity to the broken distal 

 end of the bone. Between this curve and the outer edge of the anterior surface is a 

 narrow external surface whose sides run nearly parallel at a distance of 3 or 4 mm. 

 apart along the lower three-quarters of the bone. 



The ulna of Palceoprojpithecus is a short stout bone, broken and apparently abnormally 

 enlarged at its distal end (text-fig. 37). Its proximal end bears a curious resemblance 

 to that of the ulna of Megaladapis just described. The greater sigmoid cavity is more 

 distinctly divided into two trochlear surfaces of articulation, and the coronoid process is 

 somewhat broader in the transverse direction. The shaft of the bone is rather stouter 

 in actual dimensions than that of Megaladapis, the under surface being much more 

 rounded in section. The angles limiting the various surfaces are less clearly defined, 

 and some of the areas for muscular attachment are rougher in the shorter bone. 



It may be of interest to compare the radio-humeral index of Megaladapis and 

 Palwopropithecus with that of the Simiidfe and Hominidse. This index is derived 



from the formula 



^ ^ RXlOO 



Index =: — TT — • 



In the case of Megaladapis the average lengths of three humeri and three radii 



