NO. 166G. OSTEOLOGY OF CAMPT0SAURU8—GILM0RE. 245 



The articular ends of the opposite sides are separate and when in 

 position unite more especially with the anterior than with the poste- 

 rior vertebra. The opening between the branches is proportionately 

 more elon*rate(l, and the free end is thin and expanded into a broad, 

 knife-like end. The chevron found articulated between quarry num- 

 bers 2"20 and 221 of the distal series is 52 mm. in length. This would 

 be the twenty-fourth of the series counting- from the sacrum. The 

 twenty-eighth is 45 mm. (see ch, fig. 19) in length, and the thirty- 

 first is only 25 mm. The free end is rounded from the lower margin 

 of the opening up to the dorsal border, as a thin, sharp keel, well 

 nhown in eh, fig. 19. In a rudimentary form they appear to have 

 ])ersisted as far back as the thirty-sixth caudal, as indicated by im- 

 perfectly developed chevron facets on the centra. 



THE RFBS. 



In Camptosaiirus there are present cervical, dorsal, sacral, and 

 caudal (?) ribs. Excei3ting the atlas, all of the cervical vertebrae, as 

 shown by the distinct tubercidar and capitu- 

 lar facets, bear double-headed ribs. ^' 



Cervical ribs. — The capitulum is in all 

 cases carried on the longer of the two an- 

 terior branches. This branch, w^hich is com- c-'^ 

 paratively short on the anterior cervical ribs, ''^^^ 'irS^r^.r^^ 

 gradually lengthens posteriorly, being con- tosaueus browxi. holo- 

 siderably produced on the eighth and ninth ^^g*^ ^^ .^^i ^^^ ^~^~'. 

 of the series (see r, fig. 21). The posterior side view; c, capitulum; 

 branch terminates as a somewhat rounded. *' '^'^'^^^'^'^u^u^- 

 pointed end. As shown by the single facets on the jDosterior ventral 

 surface of the intercentrum of the atlas (see r, fig. 12), it appears to 

 have carried a single-headed rib, as in the crocodile. 



Anterior cervical ribs pertaining to Cat. No. 5473, U.S.N.M., show 

 the point w^here the two anterior branches unite as a broad rounded 

 base with very short, pointed posterior branch (see Plate 12). 

 In Cat. No. 4282, U.S.N.M., the ribs of the eighth and ninth cervicals 

 were found articulated and in a fairly good state of preservation. 

 These are thin, flattened bones, without pronounced anterior indenta- 

 tion. The capitular process is moderately long, with convex articular 

 end, while the tubercular process is short, heavy, and has a concave 

 articular end. AVhen articulated their posterior extremities are 

 directed backward, outward, and downward, somewhat below the 

 horizontal. 



Dor-sal n5s.— -With the exception of the last dorsal, or, better, 

 sacro-dorsal, all of the other dorsal vertebrae bear double-headed 

 ribs. The ribs of the anterior portion of the thoracic cavit}^ are con- 

 siderably curved, esjiecially near their upper extremities. The 



