[Illustration FIG. 56. THE WING OF A WILD DUCK (_Anas boschas_). The upper figure shows the dorsal side of a right wing, the lower figure the ventral side of a left wing. × 1/3. (Brit. Mus.) 1. scapulars. 2. tectrices marginales. 3. tectrices minores. 4. bastard wing. 5. tectrices majores. 6. metacarpo-digitals or primaries. 7. tectrices mediae. 8. cubitals or secondaries. 9. pennae humerales. 10. pennae axillares.] In addition, a group of three quill feathers is attached to the first digit, constituting the =bastard wing= or =ala spuria= (fig. 56, 4). The =secondaries= or =cubitals= (fig. 56, 8) form a group of seventeen feathers, attached to the ulna; they are shorter than the primaries, and do not have the posterior half of the vane much wider than the anterior half. The =humerals= (figs. 56, 9 and 57, 12) form a group of eight small feathers, of varying length, attached to the anterior half of the humerus. [Illustration FIG. 57. WINGS OF A WILD DUCK WITH THE COVERTS REMOVED (_Anas boschas_). × 1/3. A. Right wing seen from the dorsal side. B. Left wing disarticulated and seen from the ventral side. (Brit. Mus.) 1. humerus. 2. radius. 3. ulna. 4. radial carpal. 5. ulnar carpal. 6. first phalanx of first digit. 7. second metacarpal. 8. third metacarpal. 9. first phalanx of second digit. 10. second phalanx of second digit. 11. remicle. 12. pennae humerales. 13. cubitals or secondaries. 14. metacarpal quills. 15. ad-digital. 16. mid-digitals. 17. pre-digital.] (b) The =tectrices= or =coverts= are short feathers, which cover over the quills of the rectrices and remiges, and clothe the body generally. Their barbules are less developed than is the case with the quill feathers, so that the barbs separate readily from one another, especially at the base of the vane. The nomenclature of the various patches of coverts on the wings is seen in fig. 56. A small patch of backwardly-directed feathers surrounding the external auditory opening are known as the =auriculars=. 2. The =filoplumes= are rudimentary feathers, consisting of a minute stem and slightly developed vane. They are left in the skin after the other feathers have been removed. 3. The =plumulae=, or down feathers, have the stem very slightly developed, while the barbs are soft and free from one another. They are distributed all over the body, not only among the contour feathers, but also over the spaces (_apteria_) which bear no contour feathers. In the young bird the rudiments of the new feathers are formed at the bases of the embryonic down feathers, and as they grow they push them out from the skin. The embryonic down feathers however remain attached to the apices of the new feathers till these have reached a length of about an inch; they are then shed. II. ENDOSKELETON.