Barrows.] 164 [April 4, 



the sole definite point of marked difference is found in the bills of 

 the adult, and our specimens show that up to a very late period of 

 development, long after all other characteristics of youth, save color, 

 have given place to adult characters, the bill of Alca torda preserves 

 its remarkable resemblance to that of Lomvia arra. 



If, now, we compare the bill of the adult Alca impennis with that 

 of the adult Alca torda, we find the latter much deeper in proportion 

 to its length, though the resemblance is very striking; if, however, 

 we compare it with the bill of a young Alca torda, two thirds grown, 

 we shall find that the bill of A . impennis is merely an enlarged copy 

 of that of A . torda, with perhaps a very slight difference in the feath- 

 ering of the nostrils, and the addition of the sulcations of the bill. 

 If such resemblances mean anything in the one case, they must in 

 the other. If now we take the young of the different members of 

 the genus Fratercula we shall find in the bills of all a strong similar- 

 ity to each other ; but if we compare them with the genus Alca, we 

 nowhere find a resemblance even approaching that of Alca to Lomvia. 



The similarity of the young bill of F. monocerata to the bills of 

 young of F. arctica and F. cirrhata, is one of the points which has 

 led me to include all these (as well as F. corniculata, the young of 

 which I have not seen) in one genus ; although I am perfectly well 

 aware that F. monocerata has hitherto almost always been allowed a 

 genus to itself. 



In gathering all the small Phaleridine forms under one generic 

 name, I have also departed from the usual custom of authors, but 

 nearly the same reasons have influenced me, which led Dr. Coues to 

 gather so many of these same species under the genus Simorhynchus. 

 He says (Proc. A. N. S. Phil., 1868, p. 35), " The various species 

 are all nearly identical in the structure of the wings, feet, and tail; 

 in the bill no two entirely agree. Each presents suae speciei charac- 

 ters in the shape of the bill ; but the very fact that this organ varies 

 so much seems to indicate that the differences are no more than of 

 specific importance." I have merely carried the principle a little 

 farther, including one more species than did Coues, viz., aleuticus. 



The bill of the young in all species of Auks is simpler than'in the 

 adult, and so far as I have been able to observe, it has a strong tend- 

 ency, in almost all, to become more slender. This would seem to 

 group the Auks about one central point, but thus far I have been 

 unable to discover the centre toward which these indications point. 

 From lack of sufficient specimens I am unable to do more than indi- 



