592 



PROCEEDINaa OF THE NATIONAL MUSEUM. 



VOL. 49. 



'■j/y-{f 



No. 8065, U.S.N.M. Proximal phalanx of digit III of the pes. 

 From Niobrara Comity, Wyoming. Collected by J. B. Hatcher, 

 1890. 



No. 8016, , and 5031. The partial skeletons of three individ- 

 uals in the American Museum of Natural History, New York, all 

 from Dawson County, Montana. All collected by Bamum Brown. 



THE VERTEBRAL COLUMN. 



The vertebral column is mtact and articulated from the anterior 

 dorsal region to very near the tip of the tail. This series may be 

 subdivided as follows: Presacrals (all dorsals) 16, sacrals 5, and 

 caudals 48. 



The number of cervicals is unknown ; probably not more than nine, 

 as hi Camptosaurus. I am inclined to the belief that the dorsal series 

 is complete as shown by the attachment of the most anterior sternal 

 rib at the extreme outer corner of the sternal bone, thus leaving no 

 room for the union of other ribs anterior to the sixteenth presacral. 

 The sacrum may bo considered definitely determined as having 

 five vertebrae. The tail lacks one or two vertebrae at the tip to com- 

 plete the series. Tentatively the ver- 

 tebral formula may be given as c9 ?, 

 dl6, s5, c50. 



Cervical vertebrae. — None of the 

 cervical vertebrae was preserved with 

 the type-specimen, but fragmentary 

 parts of several pertaining to the para- 

 type No. 7758, U.S.N.M., give a fairly 

 good idea of the chief characteristics 

 of the structure of the bones of the 

 neck. 



The centra are plano-concave, the 

 concavity of the posterior end being 

 very shallow. In contour the anterior 

 end is shield-shaped, the upper border 

 being slightly indented by the neural canal. The sides of the centra 

 below the neuro-central suture are pinched in, but to a less degree 

 than m Camptosaurus. Ventrally the centra are flattened. This sur- 

 face is rugosely roughened and extends the entire length of the ver- 

 tebra, bemg wider behmd than in front, as shown in figure 2. This 

 flattenuig of the cervicals appears distinctive of Thescclosaurus, for 

 in all other dinosaurs the ventral surfaces are either keeled or broadly 

 rounded. 



The neural arches are attached to the centrum by broad pedicles, 

 especially expanded on the anterior end^ where they extend outward 

 over the tops of the parapophysial buttresses. The neural canal is 

 large. 



Fig. 1.— Cervical vertebra of Thescelo- 



SAURUS NEGLECTUS GiLMORE. PARATYPE. 



No. 7758, U.S.N. M. AnouT J nat. size. 



ViE-WED FROM LEFT SIDE. a. Z'jg., AN- 

 TERIOR zygapophysis; d, diapofhysis; p, 



PARAPOPUYiSlS. 



