290 REPORT OF NATIONAL MUSEUM, 1890. 



always slender, and when closed forms a tube by the iuclosuro of the 

 under mandible between the flexible edges of the upper, the tip of both 

 being acuminate. The tongue is slender and very extensile, like that of 

 the woodpeckers, the two branches of the hyoid curving, when the 

 tongue is drawn within the bill, upward around the back of the skull and 

 then forward over the top of the head. Instead, however, of its being, 

 as in the Woodpeckers, solid and tipped with a barbed horny point, it 

 is hollow and divided at the tip into two slender branches, each of 

 which is fringed on the outer margin by a thin membrane. 



In all other characters, the Humming Birds possess nothing abso- 

 lutely peculiar, although certain features, shared by other groups of 

 birds, notably the Swifts (Micropodidce), are developed to an extreme 

 degree ; as, for example, the very high keel to the sternum and conse- 

 quent excessive development of the pectoral muscles, the short arm- 

 wing (humerus) and extremely long hand-wing (manus), and minute 

 feet with relatively large, strongly curved, and sharp claws. The Hum- 

 ming Birds and Swifts further agree in numerous anatomical charac- 

 ters, and there can be no doubt that they are more closely related to 

 each other than are either to any other group of birds. In fact, except 

 in the shape of the bill and structure of the bones of the face, the Hum- 

 ming Birds and Swifts present no definite differences of osteological 

 structure. 



As being probably more familiar with the anatomy of Humming Birds 

 than any other person, having made the subject one of special and 

 painstaking investigation, Mr. Frederic A. Lucas, of the National 

 Museum, has, at my request, prepared for this work a brief summary of 

 the osteological and some other anatomical characters of the Troch- 

 ilidce, which I take great pleasure in presenting herewith : 



Pterylosis. — The manner in which the feathers of a bird are arranged is termed its 

 pterylosis; and this varies in the different groups of birds, none, save the Penguins, 

 having the body completely and eA'enly covered with feathers, the plumage ordinarily 

 being distributed in well-denned patches, known as feather-tracts or pterylce,, inter- 

 spersed with bare spots called apleria. 



Comparatively little is known of the pterylosis of Humming Birds, only a few out 

 of the several hundred species having been thus described, but that of Florisuga 

 mellivora, shown in the accompanying figures, does not differ materially from what has, 

 been found in other species. Like other characters, the pterylosis of Humming 

 Birds seems to a great extent to be peculiar to the group, although both Humming; 

 Birds and Swifts agree in having the long, narrow, bare tracts down the back, and 

 under the throat, as well as a similar disposition of the feathers on the under side of 

 the body. Some of the Swifts, too, possess the bare space on the back of the neck,, 

 and, while this is usually quite short, yet in the species that makes the edible nests, 

 (Collocaliafuciphaga), and which has a very long neck, the nape tract is also long. 



There is, however, one curious feature common to both these groups of birds, this 

 being the existence of a small, naked patch near the tip of the wing, above and be- 

 low, colored black. This is not known to occur at all among Passeres, and has uot as 

 yet been found in any of our small North American species of Humming Birds, al- 

 though very conspicuous in many large southern forms, such as Campyjl»pteru3.. 



The pterylosis of all birds is more or less adaptive, having some direct relation, to 

 their habits, and this adaptation is well seen in Humming Birds. T\fi bare tracts on 



