258 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
portion. It is of moderate thickness, with a squarely truncated pos- 
terior extremity. Near the midlength a swelling outward of the 
upper and lower borders marks the point of attachment on the inner 
side of the sacral processes. The rectangular shape of the upper 
extremity of the ilium presents a marked difference from the tapering 
Ficure 33.—Right half of the pelvis of Polyglyphanodon sternbergi Gilmore, U.S.N.M- 
No. 15477, type, viewed from the right side, natural size: 1/, lium; 1s, ischium; pb, pubis. 
shape of the ilia of Cyclura and Iguana. On the lower half of the 
‘ anterior border above the acetabulum, a heavy truncated process 
projects prominently upward and forward. 
At the proximal end the heavy acetabular portion joins the ischium 
and pubis to form the subovate acetabulum, as shown in figure 33. 
Ischium.—In articulated position the ischium extends almost di- 
rectly downward and inward. Below the proximal end, which con- 
tributes to the formation of the acetabulum, the shaft is constricted, 
but it immediately expands into a wide, thin blade that is especially 
extended anteriorly as a tapering extremity. The distal end meets its 
fellow of the opposite side on the median line. None of the available 
specimens shows coalescence along this union, although in aged indi- 
viduals such a union may be expected. In shape the ischium is iguanid- 
like in all particulars, resembling Cyclura more closely than the ischium 
of Jguana. 
Pubis—The pubis extends downward, forward, and inward from 
the acetabular end, and meets the pubis of the opposite side on the 
median line by a short symphysis. This inner end, however, is not 
expanded as in Cyclura. The upper posterior border is rounded and 
thickened from opposite the pubis foramen to the symphysis, forward 
of which the bone is very thin. Much of this thin portion is missing in 
all the pubes present, being most complete in specimen U.S.N.M. No. 
15816 (see pl. 25). Near the acetabular end the bone is perforated 
