. :'* MEMOIRS OF THE CARNEGIE MUSEUM 



it is usually transversely perforated by an oval foramen of some size. Above its 

 anterior concave articular facet the margin is sharp, the corresponding posterior one 

 being rounded. In the more expanded part below this latter margin, we find the 

 numerous pneumatic perforations that lead into its interior parts. The large 

 pygostyle of an Albatross is triangular in outline, and the caudal vertebrae of one 

 of these birds bear but slight resemblance to those bones in Fregata. 



A number of anatomists in various places have already invited attention to the 

 striking peculiarities of the sternum and shoulder girdle of the species we here have 

 under consideration (PI. XXX., Figs. 50 and 51). 



In the specimen at hand, I find that the symphysis of the furcula is extensively 

 coossified with the fore part of the carina of the sternum, while its upper clavicular 

 extremities are in a like manner very completely fused with the mesial aspects of 

 the summits of the coracoids, upon either side. The sternal ends of these latter 

 bones form free articulations with the sternum, and the scapula? are also freely articu- 

 lated each with the corresponding coracoid. This description, it will he seen, differs 

 from what Newton found in a specimen of Fregata, and he says, " In one very re- 

 markable way the osteology of Fregata differs from that of all other birds known. 

 The furcula coalesces firmly at its symphysis with the carina of the sternum, and 

 also with the coracoids at the upper extremity of each of its rami, the anterior end 

 of each coracoid coalescing also with the proximal end of the scapula. Thus the 

 only articulation in the whole sternal apparatus are where the coracoids meet the 

 sternum, and the consequence is a bony framework which would be perfectly rigid 

 did not the flexibility of the rami of the furcula permit a limited amount of motion." 2 



My skeleton is from an adult bird, as no doubt the one examined by Professor 

 Newton was, and this makes the circumstance all the more remarkable. 



In Albatrosses the symphysis of the furcula also fuses with the sternum, while 

 the sternum, coracoid, and scapulae of some of those birds bear other slight resem- 

 blances to the corresponding bones in the skeleton of the Man-o'-war Bird. 



Fregata has a very short sternum, being about as long as it is broad. The body 

 above is profoundly concaved, where it shows numerous pneumatic foramina espe- 

 cially down the median portion. Either costal process is triangular, pointed and 

 lofty, and the costal borders short. They about equal in length, however, on either 

 side, the sharp-edged lateral margin. 



The rather short xiphoidal processes are situated, one at either posterior-external 

 angle of the body of the bone, and they are rounded off behind. For the rest, the 

 xiphoidal border that joins them is nearly an unbroken transverse line, exhibiting 



20 Alfred Newton, " Dictionary of Birds," Art. Frigate-Bird, Part I., pp. 293, 294, London, 1893. 



