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Show 1896.] ANATOMY OF THE HOATZIN. 619 laboratory at the Gardens in the course of m y investigations into the anatomy of birds. A number of important memoirs have appeared upon the Hoatzin, but, in the present condition of our knowledge of the relations among the groups of birds, additional details concerning the structure of a type so aberrant may prove useful. Alimentary Canal. The extraordinary crop and the general characters of the gizzard and intestines have been sufficiently described by L'Herminierx and Gadow2. Following the method which I have described in a former paper3, I dissected out the coils of the intestine and the Fig. 1. Intestinal convolutions of Opisthocomus cristatus. x, bridging-vessel divided ; y.m., mesentery of the yolk-sac vestige. great veins in a well-grown chick and in three adults. As shown in figure 1, the duodenal loop is unusually short and wide, and is much less specialized than in most other'birds I have examined. Recherches anatomiques sur quelques genres d'oiseaux rares ou peu C°Tur\ nn" ScL Nat- s6r- 2> Zoologie, viii. Paris, 1837. n J'^iilf Taxonomic Value of the Intestinal Convolutions in Birds," P- Z. S. 1889, p. 303. "On the Intestinal Tracts of Birds," P. Z. S. 1896, p. 136. 40* |