OSTEOLOGY OF POLYGLYPHANODON—GILMORE 255 
and stouter. The proximal articular facet, viewed from above, is 
subovate in transverse outline; its surface is moderately convex in 
both directions, but more especially anteroposteriorly and extending 
well backward on the posterior surface, thus indicating a more or 
less horizontal position of the bone in normal pose. There is a 
strongly developed deltoid ridge that is extended farther down on 
the shaft than in any of the Iguanidae. On the inner posterior surface 
near the upper articular end there is a roughened rugosity for mus- 
cular attachment. The anterior or ventral surface of this end is 
deeply concave. The deltoid ridge on the upper third of the bone 
when in natural pose looks strongly ventral. The articulations for 
the ulna and radius are turned strongly upward on the anterior sur- 
face of the distal end. The larger outer condyle for the ulna rises 
mostly from the ventral surface, the radial condyle is about subequal 
on both dorsal and ventral surfaces, as shown in figure 30. On the 
ventral side above these condyles the bone is excavated by a deep de- 
pression, as in Cyclura. This depression is only 
faintly indicated in 7Zguana. In the abrupt 
inward extension of the radial border the dis- 
tal end has a decided resemblance to that in 
Iguana tuberculata. The shaft is nearly 
straight and subovate in cross section. 
Measurements of humerus (in millimeters) 
No. 15566 
Greatest; length ee See 61 
Greatest width of proximal end_._____________ 27 
Greatest width of distal end_----_____________ 26 
heastsdiameter tot shafts ae 22s hee et 6 
fadius and ulna.—There are seven complete p.ooxe 31.—Left radius 
ulnae and the proximal end of an eighth and and ulna of Polyglypha- 
five perfect radii in the collection, and except nodon sternbergi Gil 
for a slight difference in size all are in close more, U.S.N.M. No. 
15559, natural size. 7A, 
Ulna, internal side view; 
B, radius, front view. 
agreement. ‘The description is based on the 
left ulna and radius of U.S.N.M. No. 15559 
shown In figure 31. 
The radius is a slender bone with subequal expanded ends. Its sub- 
ovate proximal end is cupped for articulation with the radial condyle 
of the humerus. The shaft is nearly straight and subround in cross 
section. The lower distal end is diagonally truncate to the longer axis 
of the bone (see B, fig. 31), having a slightly cupped articular end. 
The ulna is longer than the radius, with a stout olecranon process. 
Its proximal sigmoid surface is concave and extends upward on the 
