The posterior outline of the skull in the present specimen is not well preserved and the outline as given may be slightly inaccurate. The indentation figured by Jaekel in the posterior border of the skull of the type form is not present in the species under discussion.

Measurements of the Type Skull of Diceratosaurus lævis Moodie.

mm.
Length of skull along median suture 37
Length from muzzle to tip of horn 50
Width between tips of horns, estimated 40
Width of orbit 7
Length of orbit 10
Width of skull across the orbits 30
Interorbital width 6
Length of nostril opening 2
Width of nostril 1
Diameter of the pineal foramen - 1

Diceratosaurus robustus Moodie.

Moodie, Jour. Geol., XVII, No. 1, p. 67, fig. 15, 1909.

Moodie, Bull. Am. Mus. Nat. Hist., XXVI, art. XXV, p. 355, pl. lxiii, fig. 2, 1909.

Type: Specimen No. 8611 G, American Museum of Natural History.

Horizon and locality: Linton, Ohio, Coal Measures.

The present species is indicated by the left portion of a cranium representing a large individual. The characters of the skull are so clearly marked that it seems worthy of description. The presence of horns as given in the restoration of the skull ([fig. 24, B]) is based on the analogy with the other two species of this genus, in both of which horns are present. The generic determination of the species is based on the large size of the postorbital, which is essentially characteristic of the other species of Diceratosaurus.

The characters which distinguish the species from others of the genus are the large postorbitals and the small parietals, which are excluded from union with the postfrontals on account of the large size of the frontal. In the other two known species the frontal is small and the parietal comes forward to join the postfrontal. The present species exhibits a skull which is nearly twice as large as that of D. lævis and nearly three times the size of the skull of D. punctolineatus.

The portion of the skull preserved shows the cranium to have had a rather acuminate snout, not blunt as in the type species. The orbit is an elongate oval, although it has the same relative position in the skull as in the other species. The nostril is indicated by an oval depression near the anterior edge of the skull. The frontals, as indicated by the sutures present on the portion of the skull which is preserved, are fully as long as the parietals. Whether they were as wide as is represented is uncertain. The postfrontals are very small bones, the sutures of which are somewhat uncertain, although they can not be far from what is represented ([fig. 24, B]). The postorbital is large and elongate, and is distinctive of this species on account of its unusual size, although it does not attain the same proportions as in other members of the genus. The parietals are elongate and narrow. The pineal foramen is represented by its lateral edge and its position is about midway of the longitudinal diameter of the parietals. The narrow postparietal is represented by its anterior border; as restored ([fig. 24, B]) it may be too long. The tabulare, also, is represented by an anterior portion and it shows this element to have the position and form which is typical of the form Diceratosaurus lævis. Such other of the cranial elements as are indicated are based on the relations discovered in D. lævis.