SHUFELDT : OSTEOLOGY OP THE STEGANOPODES 21 3 



The carpometacarpus also presents us with the common ornithic features ; though 

 from its great pneumaticity, it is one of the Hghtest bones of its size we have ever 

 met with in the class. The pollex metacarpal forms a large triangular projection 

 at its usual site, while the shafts of the index and medius are nearly straight and 

 parallel with each other ; the former being fully six times the bulk of the latter. 

 Distally, neither one projects beyond the other, as is sometimes the case in birds of 

 other groups. 



The expanded portion of the proximal phalanx of the index digit is both per- 

 forated and riddled with pneumatic foramina of various sizes and shapes, and upon 

 both sides. This part sends down a conspicuous rounded process beyond the proper 

 shaft of the bone, while from the antero-distal aspect of the shaft itself, a similar 

 process projects forward. At the proximal extremity are two other apophyses 

 standing out from the bone, one being upon its anconal and the other upon its 

 palmar side, while the plane of the articular surface of the summit extends, to 

 some extent, over and upon each. The distal or terminal phalanx of this finger 

 is of great length ; trihedral in form ; and much scooped out posteriorly. Pneu- 

 matic foramina enter it at various points, one, somewhat elongated, even occurring 

 at its apex. The pollex digit is not more than two thirds the length of the one 

 just described, and its posterior aspect, instead of being scooped out, is very sharp 

 and prominent ; and this border in the still smaller phalanx of the medius digit, 

 has upon it a low tuberous apophysis for muscular attachment. None of these ter- 

 minal joints of the fingers appears to bear claws at their extremities. 



The Pelvic Limb. — Feebleness of a very marked character stamps every bone of 

 the lower extremity in Fregata. The skeleton here is, moreover, lai^ely non-pneu- 

 matic. It is, apparently, only the femur and proximal moiety of the tibio-tarsus 

 that enjoys that state at all. The former bone is quite as pneumatic as the humerus 

 of the arm, while the portion of the tibio-tarsus mentioned appears to be only 

 moderately so. 



The /emit?' is short and bulky, with its head very distinctly sessile, and its upper 

 part markedly scooped out for the insertion of the round ligament. The trochan- 

 terian ridge does not rise above the articular summit of the shaft, and it is broad 

 and flat in the antero-posterior direction externally. Below these parts extends the 

 short, straight, cylindrical shaft, more or less strongly marked by the usual muscular 

 lines. The condylar portion or distal end is weakly developed, though all the char- 

 acters common to the femora of most birds are present. A fibular notch is well 

 defined, and the external condyle is placed lower down on the shaft. Both the 

 popliteal fossa and rotular channel are very shallow ; the latter, it may be said, 



