30 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 66 



are present in front of the posterior epiphysis, but the antero- 

 inferior ones are somewhat smaller. Between these facets the in- 

 ferior surface of the centrum is grooved. 



The neural arches of the eighth caudal (pi. 10, fig. 2) are rather 

 low and the neural canal' is small and ovoidal. Short transverse 

 processes (pi. 12, fig, 2) are present; their extremities are obliquely 

 truncated. Both pairs of inferior facets for the chevrons (pi. 13^ 

 lig. 2) are situated on prominent protuberances. These articuliir 

 surfaces are obliquely placed on the protuberances and slope upward 

 and outward. The depression between these facets is deeper than 

 that on the fifth caudal. On this caudal and on the tenth the 

 prominence of these protuberances in conjunction with the outward 

 curvature of the rudimentary neural arches emphasize the con- 

 cavities above and below the transverse processes. 



The tenth caudal (pi. 10, fig. 3) is characterized by a lower neural 

 arch, smaller neural canal, and rudimentary transverse processes. 

 In cross section this vertebra would appear almost pentagonal. 

 Behind the transverse process (pi. 11, fig. 3) there is a well-defined 

 groove which curves downward and reaches the ventral face through 

 the depression between the anterior and posterior facets for the 

 chevron bones. Between these facets (pi. 13, fig. 3) there is a broad 

 elongate concavity. This vertebra is noticeably broader anteriorly 

 than posteriorly. Both epiphyses are missing. 



As compared with the tenth caudal, the fourteenth (pi. 10, fig. 1) 

 is somewhat shorter, more rounded, and lacks a complete neural 

 arch. Near the middle and inside of the low ridges which represent 

 the rudiments of the neural arch, there is an orifice for each verte- 

 brarterial canal. No trace of the transverse process is retained on 

 either lateral face of the centrum. In its place there is a mesial 

 depression which corresponds in function. with the more evident 

 groove on the tenth caudal. No facets for the chevrons are present. 



The eighteenth caudal is strongly flattened dorsoventrally. The 

 anterior epiphysis is thick with a convex articular face. The 

 posterior epiphysis is missing. Near the middle of the dorsal face 

 there are a pair of orifices for vertebrarterial canals which pierce 

 the centrum in a dorsoventral direction and emerge ventrally. There 

 is an oval longitudinal depression between their orifices on tlie 

 ventral face. The centrum is irregular in outline and is more 

 noticeably porous than any of the preceding caudals. The lateral 

 faces of this caudal are nearly vertical in contrast to the rounded 

 appearance of the centra of the anterior caudals. The anterior and 

 posterior faces of the centrum swell out and consequently the 

 epiphyses of this caudal acquire a slightly different shape from the 

 others. 



