[64]. This Bulletin, Vol. VII, p. 33.
[65]. For an excellent review of the races of H. unalascæ, by Mr. H. W. Henshaw, see this Bulletin, Vol. IV, p. 134. Several errors, perhaps typographical, are apparent in the tables of measurements given in this paper. For example, the bill of var. pallasi is said to average .53 inch, whereas the largest specimen of that form is afterwards credited with a bill of only .51. Again, var. nanus (i.e., unalascæ) does not appear from the table of extreme measurements to have been found with a smaller bill than .49, though it had previously been said to average .48. The difference in length of bill exhibited by the three races of this species is almost microscopic. A much more tangible character, not mentioned by Mr. Henshaw, lies in the disproportionate slenderness of the bill of the western varieties. In a rather large (wing 3.67) example of unalascæ before me, the bill measured across the base of the culmen is but .20 wide, while in a specimen of var. pallasi of the same site it is .25 wide.
[66]. Bull. Nutt. Ornith. Club, Vol. VI, pp. 225–235.
[67]. Descriptions of the various pigments may be found in:
Krukenberg, Dr. C. Fr. W.; Vergl.-phys. Studien, 1 R, v. Abth. 1881, SS. 72–99, u. 2 R, 1 Abth., 1882, SS. 151–171.
Bogdanow, A., Note sur le pigment des touracos. Compt. rend., T. LIV, 1862, pp. 660–663. Études sur les causes de la coloration des Oiseaux. Compt. rend T. XLVI, 1858, pp. 780, 781
Church, H. H., Researches on Turacine, an animal pigment containing copper. Chemical News, vol. XIX, 1869, No. 496.
Blasius, W., A. D. Sitzungsb des Vereins f. Naturwiss, zur Braunschweig. Braunschweigische Anzeigen, 1877, Nr. 29.
[68]. Annals N. Y. Lyceum Nat. Hist., Vol. XI, p. 136.
[69]. Hist. N. A. Birds, Vol. I, 1874, pp. 297–298.