2 4 ] 
RECORDS OF W.A. MUSEUM. 
than in the figured bones of P. mitchelli, but the ecto-tuberosity 
has an outline that approaches that of the platyrhine species. The 
ridge that extends about two-thirds along the inner surface of the 
shaft is only weakly developed compared with the striking ridge 
shown in the figures of the bone taken from P. latifrons. The 
“predeltoid ” and the “deltoid” ridges are less prominent than in 
either of the figures, P. latifrons and P. mitchelli ( platyvhinus ) ; the 
latter is even somewhat rounded, lacking the sharp profile which is 
so pronounced in the figures. The possible youth of the animal 
may account for this, although the rugged nature of the whole mass 
forming the prominence would not suggest this fact. 
The “ supinator ridge ” is best seen in the left humerus, and 
has the straight outline associated with latifrons, against the curve 
that seems to characterise the other group. It is very slender at 
its proximal end, but gains rapidly in thickness to form the 
ectocondylar triangular surface at the distal end of the bone. The 
arch of the bone that stretches from the shaft to the entocondylar 
angle or process is more slender even than is usual in P. mitchelli. 
The distal articular surfaces are distinctly seen, and again 
approach the platyrhine type, although the difference between the 
two species is very slight, and hardly to be noticed in a cursory 
examination. 
The usual extraordinary thinness of the bone above the 
ulnar division of the distal articular surface is somewhat obscured 
by matrix. 
The following measurements were made : — 
P. Platyrh . 1 
Mammoth 
Cave. 
Approximate length . . 
113 mm. 
113mm. 
Width of shaft at its proximal third 
24 mm. 
21mm. 
Antero-posterior thickness . . ... 
14.5mm. 
14mm. 
Long diameter of head and greater tuberosity 
42 mm. 
36mm. 
Short diameter across head 
? 
15mm. 
Width of distal end of humerus . . 
51 mm. 
46mm. 
The radius of the right fore-limb is present. As it varies so 
much from the bone figured by Prof. Owen (on Plate ci., loc. cit.) , 
it is advisable to describe it more fully The bone is very slender 
and much more curved than the example figured by Owen. The 
!De Vis, Proc. Lin. Soc. N.S. Wales, Vol. VI. for i8gi, p. 240, etc., and 
Owen, loc. cit. (figs.) ; chiefly the latter work. 
