36 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



The neural canal is relatively small tlu'oughout the cervical series. Tlie pre- 

 and post-zygapophyses are wide apart and have large, flattened articular surfaces. 

 The pre- and post-zygapophyses gradually draw nearer to one another antero- 

 posteriorly. In other words, the zygapophyses of the ninth cervical, though a 

 much larger vertebra than the third, are as near together antero-posteriorly as in 

 the latter. 



The neural spines of the anterior cervicals are high, quadrangular, plate-like 

 processes, with slightly expanded extremities. These become narrower antero- 

 posteriorly and wider transversely, so that on the eighth and ninth cervicals the 

 spines are about equal in both diameters, and somewhat shorter than those of the 

 anterior portion of the neck. The anterior and posterior surfaces of the two latter 

 are rugosely roughened. 



In the anterior half of the neck there are angular cone-shaped pits on the 

 anterior side at the base of the spines between the zygapophyses which become 



shallower and shallower as the posterior 

 cervicals are approached, entirely disappear- 

 ing on the ninth cervical (fig. 20). 



The combined length of the nine vertebrae 

 when articulated measured along the curve 

 is about 780 mm. In the larger individual 

 (No. S367), thi.^ same measurement is S60 

 mm. 



Above each postzyga])0])hysis on the an- 

 terior cervicals is developed a blunt spur- 

 like projection of bone that extends back- 

 ward, overhanging the articular surface. 

 This spur reaches its maximum develop- 

 ment on the sixth cervical, l)ut reduces in 

 size posteriorly: the sixth is the last one 

 showing it overhanging: and in the ninth it 

 KAL spine; z, anterior zygapophysis; z\ posterior stoj^s well forward of the underlying articu- 

 zYGAPopHYsis. ,_^^ surfaccs, only a vestige remaining. The 



greatest development of this spur coincides with the change from the wide to the 

 narrow spinous processes. 



Borsal verte})rae.—?i])Qcimei\ No. 4734, U.S.N. M., has an articulated series of 

 14 dorsal vertebrae, but since many of these lack protions of their neural processes, 

 the detailed description of these vertebrae is largely based on the excellent supjile- 

 mentary "material furnished by the somewhat larger individual catalogued as No. 

 8367, U.S.N.M. This specimen has 10 dorsals present, all in a splendid state of 

 preservation. These arc found more or less disarticulated, (fig. 21), but the manner 

 in which the zygapophyses articulate indicate that seven of them represent a con- 

 tinuous series commencing with the sixth dorsal and continuing posteriorly. The 

 first, second, fifth, and twelfth dorsals appear to be the ones that are missing. The 

 third and fourth were found articulated with one another. 



Fig. 20. — Ninth cervical vertebra of Antrodemus 

 valensLeidy.no. 4734, U.S.N.M. Jnat. size. Viewed 



from front, d, DIAPOPHYSIS: p, PARAPOPHYSIS; 4, NEU- 



