BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



Comparative Measurements of Antrodemus and Ceratosaurus Skulls. 



A ntrode- 



mus 

 No. 4734 

 U.S.N.M. 



Cerato- 

 saurus 

 No. 4735 

 U.S.N.M. 



Greatest length of skull, taken at center 



Greatest length of skull, taken at side 



Least transverse diameter above center of orbits 



Greatest expanse of nasals at center, acro.ss rugosities 



Greatest width of skull across quadratojugal 



Distance from anterior border of orbit to anterior extremity of premaxillae 



Distance from distal end of quadrate to top of skull 



Height of skull at center of lachrymal 



Height of skull at center of maxillary 



Height of skull taken at center of anterior nasal opening 



Height of skull with lower jaw, measurement taken at posterior border of orbit 



Antero-posterior diameter of orbit at center 



Vertical diameter of orbit at center 



Antero-posterior diameter of anterior nares 



Length of dental series, left maxiUarj^ 



Length of dental series, right premaxillary 



550 



620 



140 



63 



395 

 280 

 235 

 210 



310 

 70 



130 

 82 



350 

 61 



LOWER JAW. 



Plates 17, 18, and 26, fig. 2. 



Both rami of the lower mandible are present. The left, having been removed 

 from the rock, permits examination of all aspects, while the right ramus remains 

 in the matrix articulated with the skull, as shown in figure 1, plate 17, and presents 

 only the outer surfaces. The left ramus has been slightly restored and many of 

 the sutures are indistinct. The right ramus as seen in figure 1 , plate 1 7, shows plainly 

 the displacement of the elements of the hinder portion, but taken together these 

 rami enable one to work out quite accurately the extent and relationship of the 

 various bones composing the jaws. Hay' has described the ramus of Ceratosaurus, 

 but I propose to supplement his brief account with a more detailed description of 

 the several elements. 



Dentanj (d.). — The dentary is long, relatively slender, compressed trans- 

 versely, and contains alveoli for 15 teeth. The depth of the dentary increases 

 gradually in a posterior dkection, reaching its maximum vertical diameter inune- 

 diately anterior to the external mandibular foramen. This measurement at the 

 fifth tooth from the front is 63 mm. and at its deepest diameter 103 mm.; at the 

 former point it has a transverse width of 21 mm. 



The anterior end of the dentary is rounded and not so truncate as in Antro- 

 demus. The union of opposite rami was probably membranous, there being no 

 indication of symphysial contact. The alveoli are separated by thin alveolar septa, 

 which internally expand into intermediate "rugosae" (fig. 53). These are not 

 so well differentiated as in Tyrannosaurus. A longitudinal groove at the base of 

 these rugosae for the dental artery gives off side branches to the lower portion of 

 each tooth, though small foramina. 



1 Proc. U.S. Nat. Mus., vol. 35, 1908, pp. 362-363, fig. 4. 



