94 BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



insertion of several dorsal vertebrae, which obviously throws the animal out of 

 balance (see upper figure pi. 27). A preliminary sketch restoration of Ceratosaurus 

 found among some drawings made for Professor Marsh, shows fewer presacrals 

 which made a better proportioned animal than was his final restoration which has 

 been so widely published. • 



In order to place on record all of the evidence relating to the primary association 

 of the various elements of the vertebral column of the type specimen of Ceratosaurus 

 nasicornis, a complete list of the free and articulated vertebrae is given below: 



Atlas, axis, third to ninth vertebrae, inclusive, found articulated with the 

 skull. The tenth is entirely restored in the mounted skeleton. The eleventh to 

 the sixteenth, inclusive, were articulated. The remaining presacrals, that is, from 

 the nineteenth to the twenty-third, were articulated with the sacrals, they in turn 

 with the first sixteen caudals. The seventeenth to the twenty-sixth caudal, inclu- 

 sive, were articulated. The twenty-seventh is restored. The twenty-eighth was 

 found separated from the matrix, so there is no clue as to its original association. 

 The twenty-ninth to the fifty-first were articulated. 



Atlas (at.). — The atlas in Ceratosaurus consists of the usual four elements, the 

 intercentrum, two neurapophyses, and odontoid process. The intercentrum viewed 

 from the front, (fig. 5, pi. 19), is a subquadrangular block-like bone, the median 

 anterior face being hollowed out for the reception of the occipital condyle of the 

 skull. The superior median surface is deeply concave, especially on the posterior 

 side which receives the forward end of the odontoid in the articulated neck. On 

 either side of the median depression, beveled surfaces that look upward and outward 

 receive the pedicels of the neuracentra. 



The posterior view (fig. 3, pi. 19), presents a nearly vertical face for articulation 

 with the hypocentrum of the axis. The median ventral surface is shallowly con- 

 cave transversely, on either side of which are facets for the articulation of the 

 cervical ribs. 



The neurapophyses articulate with expanded pedicals upon either side of the 

 neuracentrum. These articular ends have three faces that meet at obtuse angles. 

 The posterior face looks downward and articulates with the neuracentrum as does 

 a smaller posterior face which looks backward and downward and is partially 

 apposed by an upwardly projecting spur of the intercentrum, while the largest face 

 looks downward and forward and contributes to the formation of the cup for the 

 condyle (figs. 3, 4, and 5, pi. 19). Just above the neck-like constriction of the 

 pedicel the neurapophyses gives off two processes, a short thin curved portion directed 

 inward which with a similar process of the opposite side forms the subcircular 

 openings for the passage of the spinal cord. The neurapophyses did not meet on 

 the median line. The postzygapophysial processes extend well backward, their 

 posterior ends being directed away from the median line (figs. 1, and 2, pi. 19). 

 On their interior surfaces at a point about midway between the two ends well devel- 

 oped postzygapophyses are present for articulation with the axis. The odontoid 

 is firmly coossified with the axis, (fig. 10, pi. 19), in this individual though doubtless 

 it will be found to remain free in younger specimens. It is a small bone with the 

 upper surface slightly concave, having a rounded and bluntly pointed anterior end 



