504 HARRY GOYIER SEELEY ON THE 



and the base is rounded, with a narrow median furrow. The arti- 

 culations of the centrum are oblique, looking downward and for- 

 ward; the anterior one (fig. 22) is concave from above downwards, and 

 shows a less concavity from side to side. The posterior articulation 

 (fig. 21) is evenly convex, somewhat compressed from side to side, 

 broader above than below ; it is ± inch deep, and T 3 ^ inch wide supe- 

 riorly. On the middle of the side of the neural arch, on a line with 

 the base of the neural canal, is a slight eminence indicative of a rudi- 

 mentary transverse process. The zygapophyses are broken away, but 

 extended far forward, and were elevated to the upper border of the 

 neural canal. The neural arch in front is wider than the centrum ; 

 posteriorly it is compressed and narrower than the centrum. There 

 appears to have been a slight neural spine ; but it is broken away. 

 As preserved the vertebra is -^ inch high. The neural canal is 

 small, but is larger in front than behind. 



The vertebral column, as a whole, is unlike that of any existing 

 bird ; but its affinities with members of the natatorial tribe admit of 

 no question. 



The Pelvis. (PL XXYI. fig. 23.) 



Only one fragment has come under my notice ; it is in the Museum 

 of the Geological Survey, and had already been identified by Mr. E. 

 T. Newton, F.G.S. I am indebted to Professor Huxley for the op- 

 portunity of studying this and other bird-bones in the Geological- 

 Survey Museum. The ilium is large and deep, the acetabulum 

 is perforated, and the small, but distinct, public and ischiac bones 

 are directed backward. 



The specimen is a fragment of the left ilium (fig. 23 a) with the 

 ischium broken short, and an indication of the pubis. The acetabulum 

 is T 9 ^-inch wide ; it is subcircular, and is perforated as in living birds, 

 the perforation being apparently nearly | inch wide. The external 

 surface of the ilium is smooth ; but the posterior margin of the aceta- 

 bulum is elevated considerably, as in existing birds, the anterior 

 margin being similarly depressed. The pubis (fig. 23 b) is seen on the 

 internal side of the fragment not to be blended with the ilium, but to 

 be separated by a short straight suture directed upward and backward. 

 The pubis is directed backward, but forms the inferior anterior mar- 

 gin of the acetabulum ; it is slender, -^ inch wide, subquaclrate in 

 section, with the external and internal anterior sides converging in 

 a sharp anterior marginal ridge ; consequently there are also poste- 

 rior, external and internal ridges. As preserved, the pubis is T 9 ^ inch 

 long ; it has a large medullary cavity. The ischium (fig. 23 c) is 

 more slender and more circular in section ; it forms the inferior 

 posterior part of the margin of the acetabulum ; is flattened ante- 

 riorly, and directed backward at the same angle as the pubis, from 

 which it appears to be entirely separated : as preserved, it is \ inch 

 long. The ilium is remarkably thin ; it is compressed above and 

 behind the posterior acetabular thickening, above which (as pre- 

 served) it extends for T 7 -g- inch. The length of the specimen is about 

 1 inch. 



