228 



n>TKOLOGY OF ANSERES. 



side and bent very slightly in the anterior direction. About its middle, 

 on the posterior aspect, there is a prominent muscular tuberosity, and 



other lines or scars for muscular insertion 



are evident. Of the condyles the outer one 

 is the lower, and it is profoundly cleft for 

 the fibular head. 



The popliteal depression is represented 

 by a characteristic conical pocket just above 

 the internal condyle on the posterior aspect. 

 The rotular channel in front is also deep, 

 but does not extend up the shaft a great 

 distance. 



From this same specimen I have illus- 

 trated the patella of this Merganser else- 

 where (Proc. U. S.Nat. Mus., Vol. vn). It 

 is seen to consist of two segments, with an 

 oblique groove in the cartilage connecting 

 them. Through this the tendon of the 

 ambieus muscle passes. 



Tibio-tarsus has a straight shaft that, un- 

 like the femur above it, is somewhat com- 

 pressed from before backward. At its proxi- 

 mal extremity we find a cnemial process 

 reared above its articular surface for the 

 femur. Prominent cnemial ridges occupy 

 the anterior aspect of this, as usual. Of 

 these the procnemial ridge is the higher 

 and extends the lower on the inner side of the shaft. 



The distal end of tibio-tarsus presents nothing peculiar. The groove 

 anteriorly is deep, and the osseous bridge that spans it is thrown directly 

 across. The external condyle is the broader in front, and its outer 

 aspect is in the same plane with the side of the shaft, while the corre- 

 sponding surface of the inner condyle lies beyond the plane of the shaft, 

 for its own side. 



Behind, these condyles still continue to be parallel to each other, but 

 separated by an intercondyloid concavity that from its shallowness is 

 scarcely worthy of the name, while the condyles themselves really merge 

 into a broad, articular surface in this locality. 



The fibula, when articulated, is found to rise above the summit of the 

 tibia and project beyond it posteriorly. Its head is compressed from 

 side to side, which gives it a very short, transverse diameter, while its 

 anteroposterior one is fully three times as long. The articulation with 

 the fibular ridge on the side of the tibio tarsal shaft exceeds in length 

 that portion of the bone that projects above it, and equals in length 

 the slender portion that is found below. The connection between the 

 bones along this ridge is of a ligamentous nature, and the distal fibular 



Fig i>. Left tarso-me tatarsus ; an- 

 terior view, ilergus serrator. (Speci- 

 un'ii 16626, Smithsonian collection.) 



Fig. 10. Same boneseen l'i on> below. 



Fig. 11. Corresponding bone from 

 Somateria dresseri. (Specimen 16989, 

 Smithsonian collection. j 



Fig, 12. Suiii^ bone as Fig. 11, seen 

 from below. All these figures life 

 si/c Drawn by tho author from the 

 specimens. 



