216 MEMOIRS OF THE CARNEGIE MUSEUM 



the corresponding bones of the skeleton of any species of Cormorant with those of 

 the skeleton of Anhinga. 



On the other 'hand, and by similar methods, there is no disguising the kinship 

 existing between Phalacrocorax and Sula, although the gap between these genera is 

 somewhat greater than the one standing between the Cormorants and the Anhingas. 



Pelicans of the genus Pelicanus are aberrant forms which, as osteologically indi- 

 cated, have varying relations with all three genera thus far mentioned. They are 

 however, apparently more nearly related to Sulidse than they are to the Cormorants. 



From the Pelecanoidea the passage to the PhdeiJiontoidea is not far to seek, for 

 upon comparing the corresponding bones in the skeleton of such a Gannet as Stila 

 hrewsteri with those of Phdethon flavirostris we are at once confronted with so many 

 points of similarity as to leave no doubt in our minds that it is between the 

 genera and families represented by such species as these that the linking of the two 

 groups takes place. 



This is important, for in another direction we are led, on the one hand, through 

 Phdethon to the suborder Longipennes, and on the other to the suborder Tubinares ; 

 Phdethon flavirostris having some osteological characters that strongly suggest larine 

 affinities, and still more that bring to mind the skeleton of a Pufflnus. 



Their distinct maxillo-palatines, their perforate nostrils, their hardly coalesced 

 palatines, their four-notcheds ternum, and their ilia widely separated from the 

 "sacral crista," taken in connection with numerous other important skeletal char- 

 acters, fully entitle the Tropic Birds to rank as a superfamily — the PnAitTHoisr- 

 ToiDEA as given above. 



There can be no doubt about Fregata, for the skeletal characters seen in its skull, 

 its sternum and shoulder-girdle, its pelvis and limbs, and in its trunk skeleton, as 

 we have in detail described them above, stamp it at once, not only as being a form 

 having man}?^ skeletal characters completely at variance with those found in average 

 steganopodous birds, as Cormorants and Gannets, but as a type likewise for which 

 a superfamily must be created, in order to show that these striking departures are 

 fully appreciated by the student of its osteology. As indicated in our scheme 

 above, this superfamily may be designated as the Fregatoidea. 



The pelvis in Fregata is decidedly more like the pelvis in Phdethon than in other 

 Steganopodes. In its pelvic limb-bones, which are extraordinarily short and otherwise 

 weak, as compared with the very lengthy pectoral ones, and the size of the rest of the 

 bird, it stands quite unique in the suborder to which it belongs. More remark- 

 able than all, however, are the many characters in its skull, which powerfully re- 

 call the Albatrosses among the Tubinares. These are so evident that one is almost 



