236 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
Septomaxillary—tin the right nareal opening a small irregular 
shaped bone (sma, fig. 16), in contact with the inner side of the — 
maxillary, is tentatively regarded as being the septomaxillary. 
Prefrontal—The prefrontal (pf) is a subtriangular bone whose | 
posterior extremity along the side of the frontal terminates in front 
of the orbital center. Anteriorly, the bluntly pointed end is wedged 
in between the upper and lower posterior branches of the maxillary. 
The prefrontal does not have the usual contact with the nasal bone, 
being entirely separated from it by the interposition of the slender 
maxillary process. Ventrally it articulates with the lachrymal. 
Postfrontal—The postfrontal (ptf) is a triradiate element that 
articulates about equally with the parietal and frontal extending 
across their line of junction (see fig. 17). On the left side of the | 
type skull, the postfrontal displays a squamous sutural border for | 
union with the postorbital which looks downward and forward. On 
the right side, however, no trace of this sutural junction can be 
detected, a condition suggesting that in old individuals these two 
bones might become fully coalesced. 
Postorbital—That there was a distinct postorbital (po) bone in 
Polyglyphanodon is clearly indicated in the paratype, U.S.N.M. No. 
15816, where the sutures delimiting this element are plain on both 
sides of the skull. It fills the interspace between the postfrontal 
and jugal, its anterior edge contributing much to the orbital border, 
as shown in figure 16. Posteriorly it unites by squamous suture with 
the squamosal, tapering out to a slender pointed process that hes 
upon the top border of the squamosal. 
In some lizards the postorbital is fused with the postfrontal 
(Ardeosaurus), but according to Siebenrock it is entirely absent in 
Crotaphytus and most Agamidae. 
Lachrymal—tThe lachrymal (da), viewed laterally, is narrow and 
elongate dorsoventrally and in articulated position is wedged in be- 
tween the jugal, maxillary, and prefrontal bones. Much of its outer 
surface forms a prominent diagonal ridge, which is a continuation 
of the upper jugal border. A large lachrymal foramen perforates 
the bone, the external opening of which is shown within the anterior 
rim of the orbit (see fig. 16). 
Jugal—The jugal (j) is deep and massive, with a long tapering 
spur that projects backward and downward from its posterior angle. 
This spurlike process is missing on the jugal of the type specimen, 
but the paratype has it completely preserved. Anteriorly this bone 
joins the lachrymal by a nearly horizontal suture, and it unites with 
the maxillary by a long, diagonal overlap. Posteriorly, its slender, 
upwardly directed process underlaps the postorbital and abuts the 
squamosal, as illustrated in figure 16. The jugal in Polyglyphanodon 
