JOS MEMOIRS OF THE CARNEGIE MUSEUM 



canal exists, unclosed as it is by the rather feebly produced parapophyses. From, 

 the third vertebra to the thirteenth inclusive, lateral vertebral canals are to be found, 

 and in the fourteenth vertebra the pleurapophysial elements free themselves as a 

 pair of ribs. It is only in the last three dorsals that metapophysial spines, of no 

 great length, extend backward from the postero-external angles of the transverse 

 processes, and in these three vertebrae, upon their dorsal aspects, a pneumatic pit is 

 found, on either side, posterior to the prezygayophyses. The mode of articulation 

 among the centra is of the common ornithic character, and one of the chief features 

 distinguishing these vertebrae is the lack of prominence, or even entire absence, of 

 projecting processes, so conspicuous in many other birds. A good example of this 

 is seen in the eighth, ninth, tenth and eleventh vertebrae, where the tendency of the 

 short parapophysial processes is to merge with the centra by means of osseous 

 bridges connecting the two ; and another is the marked absence of haemal spines. 



As near as I can judge from my specimen, the arrangement of the ribs of Fregata 

 is as follows : On the fourteenth vertebra there is a rudimentary pair, while on the 

 fifteenth there is a long, slender pair of free ribs, that are without epipleural proc- 

 esses. These are well-developed on the succeeding pair belonging to the sixteenth 

 vertebra; and this pair of ribs are the first of the series to connect with the sternum, 

 by means of rather short haemapophyses, the ribs of the dorsal series, seventeenth to 

 nineteenth vertebrae inclusive, are long, very narrow, highly pneumatic, and are 

 characterized by the unusual length of their epiplural spines. They all have costal 

 pairs of ribs, gradually increasing in length, and connecting with the sternum. 



Two pairs of pelvic ribs are seen, both lacking epipleural appendages, and the 

 ultimate pair anchylosed with the vertebra to which they belong, and with the ven- 

 tral surfaces of the ilia. The last pair of costal ribs fail to reach the sternum. 



The pelvis is broad and flattened. Anteriorly oneientire vertebra projects beyond 

 the ilia, but it is coossified in its position with the "sacrum." 



Viewed from above, we are to note that the ilia are widely separated from the 

 sacral crista, which latter are very large, rounded and depressed. Slight concavity 

 characterizes the preacetabular iliac areas, and the anterior emarginated borders of 

 these bones are very obliquely truncated from their antero-mesial angles backwards. 

 The interdiapophysial vacuities in the uro-sacral region are of considerable size, and 

 the most part they have a parial arrangement and are very large in front. 



The postacetabular areas are about equal in extent to the anterior ones, and are 

 convexed as much as the latter are concaved. Bony fusion between the ilia and 

 the vertebrae is, in all this region, very perfect, extending clear to the sacral ex- 

 tremity, and no part of the latter projects posteriorly beyond the iliac bones. 



