m. 2127. 



OSTEOLOGY OF TEE8CEL08AURU8—GILM0RE. 



595 



Passing outward from the centra the outer ends of the sacral ribs 

 are expanded fore and aft to meet one another, becoming coalesced, 

 and thus inclose a series of four sacral foramina. In Hypsilophodon 

 the sacral ribs unite with the sacrals intervertebrally throughout the 

 series, as they do in Camptosaurus. The spinous process of sacral 

 one is distinct, but those of s^, s^, and s* (shown by the impressions 

 in the rock) were closely joined and appear to have formed a con- 

 tinuous sheet of bone. The spinous process of the fifth is free. 

 Viewed laterally, these spines extend but little above the superior 

 borders of the ilia. The combined length of the five sacral centra 

 is 195 mm. 



Fig. 6.— Anterior caudal vertkbeae (5th, 6th, and 7th) of Thescelosaurus neg- 

 LECTus Gilmore. TYPE. No. 7757, U.S.N.M. § nat. size, c, Chevron; s, spinous 

 process; t, transverse process; z, anterior zygapophysis; z', posterior zygapoph- 



TSIS; 6, FIFTH CAUDAL. 



Caudal vertebrae. — Forty-eight articulated caudal vertebrae are 

 present with the type, and, as stated previously, it would appear as 

 though two or more are missing from the tip of the tail, so that in 

 Thescelosaurus the complete series would consist of at least 50 ver- 

 tebrae. The first caudal may be recognized by the absence of chev- 

 ron facets and the backward incUnation of the spinous process. As 

 in Hypsilophodon, the second caudal carries the first chevron. This 

 is indicated in the type (No. 7757, U.S.N.M.) by a mutilated frag- 



