Page:Parasaurolophus walkeri, a new genus and species of trachodont dinosaur.pdf/18

14 the supratemporal fossae. They seem to terminate laterally in points between the frontals and postfrontals (i. e., within and behind the postorbital notch, not shown in ﬁgure).

Supratemporal fossa—This opening is small and hidden under the crest: owing to the sloping character of the margins, exact measurements are difﬁcult to make, but it may be said to be about 95 mm. long and 50 mm. wide.

The mandible is of the usual trachodont type: the extreme length is 640 mm., and the depth from the alveolar margin to the inferior edge at the ﬁrst tooth is 104 mm. From the ﬁrst tooth to the anterior point on midline is 200 mm.

Predentary—This bone is small and overlaps the dentary with prominent suture. Width, 280 mm.; length, 130 mm. on midline from anterior point to line joining the posterior prongs.

Dentary—The dentary is of the ordinary type, rather strongly decurved anteriorly. The length on the inferior margin from articulation with predentary to articulation with surangular is 455 mm., and from the posterior prong of the predentary to the same point, 390 mm. Thirty-one teeth are visible in a distance of 240 mm. Still more may occur, but if so they are hidden under the coronoid process. There is evidence of at least three rows. Seven prominent foramina occur on the external surface of this bone as shown in the ﬁgure. The coronoid process is prominent and directed slightly forward: it is 50 mm. wide at midlength. Its total height cannot be ascertained as it is partially hidden under the jugal, but it rises at least 190 mm. above the inferior margin of the mandible and 90 mm. above the alveolar margin.

Surangular—The upward extension of this bone lies beneath the coronoid process with its margin almost parallel with the posterior margin of the process: the bones are separated by a deep sulcus. The suture with the dentary runs irregularly down and back to the inferior edge of the mandible.

Angular and articular—The sutures of these bones with each other and with the surangular are not visible. From