596 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 49. 



ment found in situ between the second and third vertebrae, though 

 the greater portions of the centra of these two vertebrae are missing. 

 Transverse processes are present in the first 10 caudals, whereas 

 in Ilypsilophodon the first 14 have transverse processes and in Camp- 

 tosaurus the first 12. This process on the first caudal is shorter than 

 those immediately succeeding it. They increase in length from the 

 first to the fifth, and gradually shorten posteriorly, ending abruptly 

 on the tenth, which has a length of 23 mm. All are given off from 

 the side of the centra immediately below the level of the neuro-cen- 

 tral suture (fig. 6). With the disappearance of the transverse pro- 

 cesses the length of the centra is shghtly increased and they become 



Fig. 7.— Median caudal vertebrae (24th, 25Tn, and 26th) of Thescelo- 



SAURUS NEGLECTUS GiLMORE. TYPE. No. 7757, U.S.N.M. J NAT. SIZE. 



s, Spinous process; t, ossified tendons; z, anterior zyg.vpopiiysis. 



more cyhndrical in shape (fig. 7). This increase in length continues 



back to the twentieth, and from this vertebra to the .tip the centra 



gradually decrease in this diameter. 



The spinous processes have a decided backward incUnation and 



are gradually reduced in height posteriorly, disappearing altogether 



on the thirty-sixth vertebra. Weak 

 zygapophyses persist as far back as 

 the forty-fifth. The thin anterior 

 expansion at the base of the spinous 

 process shown in figure 6 is present 

 only on the first 10 caudals. The 

 most distal caudals have short cyl- 

 inderlike centra without zygapophy- 

 sial articulation and with but slight 



expansion of the two extremities (see fig. 8). 



Chevrons. — As in Hypsihphodon, the chevrons are longer than the 



spinous processes. Their articular ends are slightly expanded antero- 



posteriorly, the free end flattened but without marked expansion. 



The first chevron is short and with a pointed distal end and rounded 



shaft. The two articular surfaces of the proximal end are separate. 



The fourth and fifth (fig. 6) are the longest of the series, but proceed- 



FiG. 8.— Distal caudal vertebrae (40th, 

 41st, and 42d) of Thescelosaurus neg- 

 lectusGilmore. Type. No. 7757, U.S.N.M. 

 J NAT. SIZE, t, Ossified tendons; z, ante- 

 rior ZYGAPOPHYSIS; Z', POSTERIOR ZYGA- 

 POPHYSIS. 



