OSTEOLOGY OF POLYGLYPHANODON—GILMORE 253 
The clavicle of Polyglyphanodon is a simple curved bar, perforated 
near its expanded lower end by a subovate fenestra. The upper por- 
tion is narrow, but the shaft gradually widens in a ventral direction. 
Approaching the fenestra the posterior border abruptly widens and 
then maintains its width to the truncated interclavicular end, as 
shown in figure 28. 
The concave margin of this 
bone is slightly thickened and 
rounded, but the opposite side is 
thin, presenting a sharp edge for 
much of its length. The posterior 
side of the distal half is hollowed 
out longitudinally. Its greatest 
length measured in a straight line Ficure 28.—Left clavicle of Polyglypha- 
from end to end is 50.8 mm. nodon sternbergt Gilmore, U.S.N.M. 
On the whole this bone bears a era ee enateune Re cy a undue 
cam view drawn as it lay in the matrix; B, 
strikingly close resemblance to the aes Canna 
clavicle of the iguanid lizard Lae- 
manctus, the chief difference being in the more dorsal placement of 
the fenestra in the clavicle of the extant form. 
Camp * was of the opinion that broadly expanded, nonperforate 
clavicles are ancestral among modern Sauria and that simple rounded 
clavicles have been shaped from these. The perforate clavicle of the 
present specimen shows that this type originated very much earlier 
than was previously known and 
to that extent does not give 
support to Camp’s conclusion. 
Interclavicle—T he inter- 
clavicle of Polyglyphanodon 
sternbergi may be described as. 
cruciform, with a bifurcated an- 
terior extermity and a long flat- 
tened posterior bar, the poste- 
rior end being obtusely pointed. 
Figure 29.—Interclavicles of Polyglyphanodon 
sternbergt Gilmore, ventral views, natural 
size: A, US.N.M. No. 15559; B, US.N.M. his element is present in 
No. 15568. four specimens, U.S.N.M. Nos. 
; 15559, 15566, 15568, and 15816, 
all being slightly imperfect. The complete cross bar is preserved only 
in U.S.N.M. No. 15816, but in this specimen it is slender, with a 
slight curve posteriorly. Forward of this bar the shaft is constricted, 
but still farther forward it rapidly widens into two flattened diver- 
gent processes that are separated on the anterior end by a wide shal- 
*Camp, C. L., Classification of the lizards. Bull. Amer. Mus. Nat. Hi 
368, 1923. . Mus. Nat. Hist., vol. 48, p. 
