■i04 ME. W. P. PYCRAFT ON THE 



are subequal, and in this respect Biziura and JErismatura agree, 

 and differ from all the species herein used for comparison, 

 inasmuch as in these the manus is by far the largest segment of 

 the wing. 



Although Biziura is a larger and heavier bird thau Somateria, 

 the wing is altogether of a more slender character ; and this is 

 most evident in the manus. The metacarpals are fragile, Mc. IT. 

 having a diameter of a little less than j2_ {^^^ while in Somateria 

 the diameter in the same region is about yL i^. ]\£c. III. is 

 represented by a long and delicate bar, separated from Mc. II. 

 only by a narrow chink ; in Somateria Mc. II. is outwardly 

 bowed and much stronger. The phalanges in Biziura are 

 much reduced. 



Although the wings of Biziura and JErismatura show the same 

 general proportions in the matter of length, it by no means 

 implies that Erismatura stands in such imminent danger of 

 flightlessness as would seem to be threatening Biziura, inasmuch 

 as it is a smaller and more active species. 



It is interesting to remark that in so far as size is con- 

 cerned there is little, at first, to indicate the degenerate condition 

 of the wing in the flightless Tachyeres. Slightly longer in the 

 humerus than Somateria, in the lengths of the fore-arm and 

 manvis TacJiyeres and Somateria agree exactly. But the bones 

 in Tacliyeres are all much thicker than in Somateria. The 

 decadent condition of this wing becomes apparent when we 

 reflect that Somateria is at least one-third smaller than Tachyeres. 



This bird, it is generally believed, loses its power of flight after 

 the first moult. But it would seem that not even the young- 

 birds fly, since Mr. M. J. Nicoll, writing to the ' Ibis,' 1904, p. 49, 

 remarks : " In most accounts of this bird it is stated that it 

 rows itself along through the water with its little wings at an 

 incredible rate. It certainly goes very fast, but practically it 

 runs in the water flapping its wings clear of it ;" and continues : 

 " The young travel through the water nearly as fast as the 

 adults, in which the muscles of the legs are enormously 

 developed." Prom this it would seem that the decay of the 

 wing began by a reduction in the size of the remiges ; later the 

 skeleton became affected. It is, however, a moot point as to 

 whether the skeleton of the wing has, as yet, iindergone any 

 appreciable change, inasmuch as in the proportions of its several 

 segments it preserves all the relations of a functional wing. 



