28 
passes downward, becoming concave and more rugose in its lower part 
with a sudden increase in the thickness of the bone. The surface for the 
jugal is roughly semicircular in outline with the curve forward. 
The antero-superior border of the maxillary is transversely narrow 
and is furnished with a smooth, shallow groove in which lay the infero- 
posterior process of the nasal directed forward below’ the hinder end of 
the nasal opening. In continuation forw’^ard of this border is a laterally 
compressed process (anterior maxillary process) which extends considerably 
beyond the main lower termination of the bone and is separated from it 
by a deep emargination (anterior maxillary notch). The postero-superior 
border of the maxilla is also narrow and supplies a very rugose sutural 
surface for the attachment of the lower edge of the palatine. In continua- 
tion backw’ard of this border occurs a posterior process betw’een which 
and the heavy, rounded end of the bone is a posterior notch of smaller 
proportions than the anterior one. The postero-maxillary process receives 
in contact internally the pterygoid as the latter passes forward to lap 
within the palatine. It is grooved below for the upper border of the 
ectopterygoid in such a manner that its termination lies external to and 
on the ectopterygoid. The posterior notch is filled by the thickened 
portion of the ectopterygoid. The postero-external surface below the 
notch is rugose, curves convexly dowm to the level of the alveolar border 
and receives in close contact the ectopterygoid and below it the pterygoid, 
the latter being overlapped by the former. The posterior end of the 
maxillary ridge is bounded above and behind by a groove into w^hich 
fits the lower border of the ectopterygoid w’here it begins its rapid posterior 
expansion. 
Although the inner face of the maxillary is flat as a whole in comparison 
wdth the outer one, the apical region is decidedly hollowed out, and there 
is a shallow concavity of the surface extending from the anterior end back 
past midlength. A conspicuous feature of this face is a flatly arching 
row^ of small, circular foraminal openings extending below the midheight 
of the bone from points above the first and last teeth. There is one 
foramen to each vertical series of teeth. Between these dental foramina 
and the alveolar border is a well-defined vascular groove of the same 
length and with nearly the same curve as the foraminal row\ In the lower 
portion of the apical concavity are tw^o foramina, one large, the other 
small, placed close together and leading downw’ard. 
There are fifty-one to fifty-three vertical series of maxillary teeth 
occupying seven-eighths of the total length of the bone, the dental magazine 
terminating closer to the posterior than to the anterior end. The external 
and internal alveolar borders are at the same level. 
Exteriorly tw^o large foramina occur beneath the protrudent base of 
the surface for the attachment of the jugal, and one, even larger, is present 
considerably in advance- of the same surface near the superior border. 
In the same general region are other small openings disposed as shown in 
Figure 12. Special reference is made to the maxillary teeth under another 
heading (page 55). 
Measurements of Left Maxillary of Edmontosauriis, Cat. Xo. 2289. 
Mm. 
Maximum length, about 436 
Length at level of alveolar borders 422 
