82 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



processes at their junction are surmounted by a stout tubqrous projection that rises 

 above the general level of the superior surface of the skull. In life this tuberosity 

 no doubt had a horny covering. This process is missing on the left side, but on 

 the right side it is largely intact. The upper borders have suffered some loss, and 

 it is not altogether certain that this process as shown in the restored skull represents 

 its true outlines. It appears quite probable that the tip was more sharply pointed 

 as in Antrodemus and not obtusely rounded as here represented. As in the latter 

 genus this bone is lightened by pneumatic cavities. 



Nasals (n.). — The nasal bones are elongate and they differ principally from 

 those of known carnivorous dinosaurs in giving support to a large transversally 

 compressed horn core on the median line. The upper two-thirds of the lateral sur- 

 face of this horn core is very rugose and furrowed with vascular grooves. The 

 smooth portion near the base of the horn has a greatest transverse width of 12 mm., 

 which is rapidly increased to 20 mm. at the point where the roughening by the vas- 

 cular grooves begins. The horn has a greatest length antero-posteriorly at its base 

 of 130 mm. and an extreme height above the nasals of 70 mm., the greatest vertical 

 diameter being posteriorly to its middle. It evidently supported a high, trenchant 

 horn, which formed a useful weapon for offense and defense. Additional material 

 is required before it can be ascertained whether this feature pertained to all individ- 

 uals of this genus or was only a sexual character. 



Immediately posterior to the nasal horn core there is a deep elongate depression 

 on the median line, as shown in figure 1, plate 18. The lateral borders above the 

 antiorbital fenestrae are notched as in Antrodemus for the reception of the anterior 

 process of the lachrymal, as may be seen in plate 18. In front of this notch the 

 outer border is slightly roughened and rounded over, not presenting a sharply raised 

 edge, as in Antrodemus. It overhangs the upper branch of the maxillary as in the 

 latter genus, and is perforated likewise by a number of pneumatic cavities. The 

 anterior ends of the nasals where they join the premaxillaries above the external 

 narial opening are missing. Posterior to the nares the nasals widen out and arch 

 over the nasal passages. In Antrodemus the lateral borders of the nasals converge 

 from the anterior border of the lachrymals to their anterior extremities, whereas in 

 Ceratosaurus they converge for a short distance and then become divergent. 



Premaxillary (pmx.). — The premaxillaries in the type of Ceratosaurus nasicornis 

 contain fewer teeth than in any other known member of the Theropoda, excepting 

 Struihiomimus. Each premaxillary has alveoli for three functional teeth. Marsh 

 has pointed out that in ' ' the genera Compsognathus and Megalosaurus of this order, 

 each premaxillary contained four teeth, the same number found in the Sauropoda. 

 In the genus Creosaurus from the American Jurassic the premaxillaries eaeh contain 

 five teeth. " Antrodemus also has five, while Orniiholestes from the Morrison, Gor- 

 gosaurus from the Belly River, and Tyrannosaurus from the Lance have four teeth 

 each. 



In this specimen the superior processes which curve upward and backward to 

 meet the nasals are missing, although indicated in Marsh's restoration of the skull 

 as being present. 



