234 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



this character being especially pronounced in the posterior dorsal 

 region (see fig. IG). The neural canal remains about the same size 

 from the fourth to the fourteenth. 



77<e fifteenth dorsal. — ^^This vertebra may be at once d'.stinguished 

 by its short centrum (see dorsal No. 15, table of measurements, page' 

 243), Avhich in No. 4282 is cylindrical in outline, with a weak ventral 

 keel. The articular ends are concave, more especially the posterior. 

 Antero-posteriorly it is the shortest of the dorsal series. The trans- 

 verse process is short, wide, and directed outward at right angles to 

 the neural process. It has weak tubercular and capitular rib-facets, 

 which show that it carried a double-headed rib. 



The sixteenth dorsal or saero-dorsal. — The last dorsal centrum 

 (sacro-dorsal) is longer and heavier than the one preceding and is the 

 most robust of the vertebral series of No. 4282 (see sd., fig. IT). The 

 two articular extremities are slightly concave, the posterior having a 

 rough, rugose surface. Antero-posteriorly the sides are deeply con- 

 cave, the inferior surface being pinched together, forming a short, 

 pronounced median keel which expands transversely at either end. 

 This vertebra in No. 1877«, paratype of C. dispar (Yale University 

 Museum), is regularly rounded in this aspect and without ventral 

 keel. On the supero-posterior angles are roughened, obliquely i:)laced 

 surfaces which give partial support to the first sacral ribs. The 

 neuro-central suture is relatively shorter than in the preceding dor- 

 sals, a groove for the exit of a nerve limiting its extent posteriori}-. 

 The arch is higher than those immediately in front, and supports a 

 weak diapophysis without parai)ophysial facet, indicating the pres- 

 ence of a single-headed rib which may have articulated with a small 

 articular area on the internal side of the preacetabular process of the 

 ilium. In No. 4282, the outer extremit}^ of this process is missing, but 

 it is plainly shown in the typical specimens of C. dispar and C. nanus, 

 Plate Vi and fig. 39. As shown in fig. 17, the prezygapophyses 

 are large and look almost directly upward. The spinous process is 

 missing on this vertebra of No. 4282, but is present in No. 1877a, Yale 

 Museum (see Plate 13). It is shown as a rectangular plate-like 

 spine rising high above the diapophysis. The superior termination 

 is thickened transversely, more especially on the anterior part of this 

 border, which is heavier than the spine that follows, and, in this 

 species {C. dispar), jorobably marks the nuiximum development of 

 the spinous processes. The greatest height of this vertebra, taken at 

 the center of the centrum, is 330 mm. The spine has a vertical 

 groove on its posterior border extending nearly to its top. The post-, 

 zygapophyses overhang considerably the end of the centrum. 



The sacrum. — In specimen Cat. No. 4282, U.S.N.M., there are seven 

 vertebrae imited by a suture in the sacral region. Of this series I liave 

 considered as sacral only those vertebrae which support true sacral 



