Maryland Geological Survey 195 



The sacral (No. 4969, U. S. National Museum) (pi. xv, fig. 5) is appar- 

 ently the second or third, and, as characterized by Marsh, is solid, as in 

 Morosaurus, but much more elongate. The surface for the rib covers 

 the anterior half of the centrum, behind which is a deep pit extending 

 slightly forward into the base of the rib facet, but which does not, how- 

 ever, extend far into the body of the centrum itself. Anteriorly, the 

 articular face is somewhat triangular, with the apex pointing downward; 

 posteriorly, it is more nearly oval. The neural arch was attached to the 

 anterior two-thirds of the centrum, so that the intervertebral foramen 

 for the exit of the spinal nerve was wide, in keeping with the great 

 width of the neural canal. 



The dimensions of the sacral are as follows : 



Length 76.0 mm. 



Anterior diameter 71.5 mm. 



Posterior diameter 67.0 mm. 



Depth of centrum 57.0 mm. 



Almost the entire caudal series is known from the centra and, in a few 

 instances, from the neural arches as well. There is no trace, however, 

 of the chevron bones. 



The anterior caudals are short and nearly amphiplatyan, wherein 

 again they resemble Morosaurus lentus. The middle and distal caudals 

 have more elongated centra, but they are still relatively short. The 

 anterior caudal (No. 5639, U. S. National Museum) (pi. xvi, fig. 3) is 

 typical, having the shortened centrum with the anterior face slightly 

 concave, the posterior one very slightly so. The facets for the trans- 

 verse processes are high so that the transverse process must have borne 

 against the neural arch to some extent. Facets for the chevron bones 

 are very slightly indicated. The dimensions of the bone are as follows : 



Length 37.5 mm. 



Breadth 71.8 mm. 



Depth 61.8 mm. 



The pedicels of the anterior caudals are stout, with prolonged pre- 

 zygapophyses. The character of an anterior caudal is shown in fig. 3. 



The caudal (No. 4970, U. S. National Museum), one of the cotypes, 

 is somewhat hour-glass shaped, amphicoelous, with the sutures for the 



