442 H. GOTIER SEELET ON MACRUROSATTRTTS SEMNTTS. 



is flatter ; and there is scarcely any trace of a ball. The greatest 

 diameter of the constricted part of the centrum is 2J inches ; 

 the neural pedicles become more elongated, measuring 2| inches. 

 After the 13th the centrums get rapidly smaller. The 15th is 

 distinctly biconcave ; the centrum is somewhat compressed later- 

 ally ; the neural canal is narrower, with a concave channel in the 

 centrum, margined by shorter pedicles. The 16th is 4 j inches long. 

 The 20th is 4 inches long, has the centrum 2f inches wide pos- 

 teriorly, and, as preserved, is 2| inches deep. The least diameter of 

 the centrum where most coustricted is 1 j inch. The articular ends 

 are greatly flattened, but slightly concave, as in many Plesiosaurs. 

 The pedicles for the neural arch remain at one inch from the anterior 

 margin; the extreme external width across the pedicles is 1J inch ; 

 the width of the neural canal is J inch ; the antero- posterior ex- 

 tent of the pedicles is 1J inch. Between No. 23, the last of the 

 Barnwell series, and 24, the first of the Barton series, a few are 

 probably lost. The Barton portion of the animal is in rather 

 better preservation, though a few of the vertebra?, which have 

 been washed with the phosphatic nodules in the mill, show curi- 

 ously how the circumstances under which fossils are collected may 

 modify their appearance. In No. 24 the centrum is 3 \ inches long, 

 and 2 inches deep in front ; the anterior articulation is deeply cupped ; 

 and the posterior articulation somewhat approximates to a ball. The 

 least diameter of the middle of the centrum is less than 1| inch. The 

 pedicles are now placed nearly in the middle of the length of the cen- 

 trum. No. 25 is 3|- inches long, with the articular ends 2 J inches in 

 diameter ; they are deeply cupped with a central deeper depression. 

 The next vertebra has the articular ends much flatter, with a trans- 

 verse depression which does not appear to result from pressure. No. 

 28 is 3| inches long, and has pits in the neural canal like foramina 

 for blood-vessels. No. 30 has the centrum anteriorly deeply con- 

 cave ; posteriorly it is subconvex with a transverse groove. No. 35 

 is 2j inches long. The posterior articulation is convex with a slight 

 central depression ; as preserved it is 1^ inch wide. The centrum is 

 compressed from side to side, measuring |- inch in least diameter ; 

 the anterior articulation is very irregular. The neural canal is 

 about | inch wide. The pedicles are compressed, i inch wide and 1 

 inch long. 



A few neural arches are preserved. They are remarkable for 

 great antero-posterior extent, compression from side to side, and 

 absence of a neural spine, the superior margin being concave from 

 front to back, and only rising two inches above the top of the 

 neural canal in the deepest specimen. In that example the posterior 

 zygapophysial facets are preserved. They are \ inch in diameter, 

 and are raised like wafers on the inferior margin of the specimen so 

 as to look outward and downward. The median posterior portion 

 of the arch is prolonged for some distance behind the facets ; ante- 

 riorly the arch is forked. Further back in the tail, where the arch 

 is more depressed, the articular facets are lost ; but the posterior 

 process, ovate in section, is still directed for some distance upward 



