OCR Text |
Show 1879.] ANATOMY OF THE HOATZIN. Ill drawing is reproduced in Mr. Perrin's memoir), the outline of the furcula and sternum, and does it as if the bird were not peculiar in the pectoral region. But as the crop occupies almost all the upper part of the breast, and by its magnitude distorts the furcula and sternum, the outline is quite incorrect. What is more, there is in the bird itself an oval area, about *75 inch long from above downwards, and *25 inch in breadth, of dense naked skin, covering the surface of the expanded upper cutaneous surface of the carina sterni. This is omitted in the drawing. The area surrounding this is unfeathered, although I find well-developed plumes in the middle line above it, Fig. 2. i!iiiiim/«iiiin,i uwidiiiii** Trachea of Opisthocomus (back view). and no trace of any longitudinal median space of any kind over the surface of the crop or neck. Opisthocomus is one of those birds in which the pterylosis is not so decisive of its affinities as in many cases, the reason being that so great an amount of the unfeathered spaces is protected by semi-plumes. May not these semiplumes in many instances be degenerated feathers ? This question has never been decided, so far as I a m aware. To our knowledge of the osteology of the Hoatzin I have no fresh |