214 MEMOIRS OF THE CARNEGIE MUSEUM 



hardly exists at all. Pneumatic foramina are always found at the base of the 

 former, immediately above the internal condyle. 



Lack of salient characters distinguishes the tibio-tarsus even more profoundly 

 than the femur. Its cnemial crest and processes are almost completely reduced, the 

 former barely rising above the nearly level articular summit of the bone. Com- 

 paratively short and quite straight, its shaft is of decidedly slender bulk, being 

 subcylindrical in form. The fibular ridge is confined completely within the limits 

 of its upper third, being but a little more than a centimeter in length. Its articu- 

 lation with that bone is very free. At the distal end we find a pretty well de- 

 veloped pair of condyles, but the osseous bridgelet in front is low down and weak, 

 indicating that the tendons too, which it is intended to hold in place, must also be 

 but feebly developed. 



The fibula is nearly complete, its lower end, of hair-like dimensions, is fused with 

 the side of the shaft of the tibio-tarsus immediately above the external condyle of 

 the latter bone. Above its proximal articulation, the fibula is of larger size, stand- 

 ing in strong contrast with the very slender straight part below that point. 



Fregata has a flake-like patella of some size, being quadrilateral in outline, and 

 marked obliquely across its anterior surface by a groove for the ambiens muscle. 

 As with the vast majority of birds, it is non-pneumatic in character. 



The tarso-metatarsus is wonderfully short and thick-set. This bone is so much 

 abbreviated in the direction of its longitudinal axis that it hardly appears to 

 possess any shaft at all. Antero-posteriorly it is flattened, while transversely it is 

 relatively broad. On its anterior surface well-marked grooves plainly indicate the 

 three metatarsal elements of which it is composed, while posteriorly the short shaft 

 is quite flat and smooth. Its hypotarsus is bulky and circumscribed, — not extend- 

 ing down the bone, — while a single central canal pierces it for the passage of the 

 tendons. This is of some size. Distally, the trochlear processes are comparatively 

 large and spreading. They all lie in nearly the same transverse plane, the inner 

 one being the lowest in position ; the outer, the highest ; and the middle one 

 occupying an intermediate place. The foramen for the passage of the anterior 

 tibial artery is peculiar, inasmuch as its lower exit is in the sulcus between the 

 outer and middle trochlear projections instead of on the back of the shaft above 

 that point, where it is usually to be found. The accessory or first metatarsal is as 

 large in proportion as in those birds where the skeleton of this limb is harmoniously 

 developed in point of size with the rest of the osseous system. All the phalangeal 

 joints of the pes are well developed, being arranged upon the plan of 2, 3, 4, 5, for 

 the first to fourth toe respectively, and were not this part of the skeleton of the foot 



