OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



31 



pressed, with a backward curvature, especially of the upper anterior border. The 

 upper portion tapers to an obtuse point. In section this part of the teeth is lenticular. 



The great irregularity in size of the teeth is due to the loss of functional teeth 

 and their subsequent replacement by young teeth which appear in various stages of 

 growth. These changes apparently went on throughout the life of the individual. 



Some of the teeth show signs of wear on the inner sides near their tips, but this 

 abrasion is only found on the fully erupted ones. Many of the detached teeth in 

 the collection are thus worn, probably from abrasion caused by the rubbing of the 

 points of the upper and lower series. 



VERTEBRAL COLUMN. ' 



The vertebral formula in Antrodemus valens Leidy as largely determined from 

 specimen No. 4734, U.S.N.M., is as follows: C, 9; D, 14; S, 5; C, 45 ±. 



The precise number of vertebrae in the tail yet remains to be determined. 

 Since the type of Ceratosaurus nasicornis shows 50 vertebrae it appears fair to 

 assume that Antrodemus had an equal number. An articulated presacral series in 

 the American Museum of Natural History, New York City, No. 666, verifies the 

 present specimen in showing that there are 23 vertebrae in front of the sacrum. 



A second specimen in the United States National Museum collection, No. 

 8367, has 18 presacral vertebrae present, nearly all in an excellent state of preserva- 

 tion. The descriptions of the vertebrae to follow are largely based upon these two 

 specimens. 



The vertebral formula of Antrodemus as compared with other Theropodous dinosaurs is as follows. 



Cervical vertebrae 

 Dorsal vertebrae . 

 Sacral vertebrae . . 

 Caudal vertebrae . 



Antrodemus. 



9 

 14 



5 

 45 ± 



Ceratosaurus. 



?9 



?14 



5 



52 



Gorgosau- 

 rus. 



?9 



?14 



5 



36± 



Tyranno- 

 saurus. 



10-9 



13-14 



5 



?53 



Ornitholes- 



Ornithomi- 

 mus. 



19? 



10 



?13 



13 



4 



5 



?39-44 





Atlas (a. in.). — In specimen No. 4734, U.S.N. M., we are fortunate in having 

 found the atlas and axis nearly in position in relation to one another, and the manner 

 of their articulation is clearly shown in figure 17. Viewed latterly, when articulated 

 with the hypocentrum of the axis, the cupped anterior surface of the intercentrum 

 looks upward and forward at an angle of 45° to the longer diameter of tbe axis. 



The intercentrum of Antrodemus may be distinguished from that of Cerato- 

 saurus by its shorter diameter antero-posteriorly, the more nearly parallel anterior 

 and posterior borders when viewed from the side, and the greater width of the con- 

 cave surface on the superior side. There are other slight differences noted, but 

 doubtless these would vary with the individual. The chief features of this bone 

 are clearly shown in figure 17. The greatest length is 28 mm.; greatest width is 

 66 mm. 



Only the neuropophysis of the left side is preserved with this specimen, and it 

 lacks portions of the anterior and posterior processes. It differs from the neura- 

 pophysis of Ceratosaurus, however, in the less transverse expansion of the articular 



