| OCR Text |
Show 1887.] OF THE WINGS OF BIRDS. 345 The remaining feathers of the wing are the coverts; they are best understood if described from the posterior margin of the wing. On the dorsal side tbe row of feathers (Plate X X X . fig. a, a) lying next the remiges are the tectrices majores, being quite definitely related to the remigeal quills, and lying close pressed upon their bases. Each remex is serial with the covert proximal to it, the cubital coverts crossing over the bases of the remiges, the metacarpal coverts lying parallel and pressed upon two contiguous remiges (cf. Plate X X X I . figs, b and c). There is a well-developed covert to every metacarpal except the first, which possesses only a very small and vestigial one, 1', which is completely hidden by a median covert, 1" (Plate XXXII. fig. 8), which in many birds functionally replaces it, the t. major disappearing. On the ventral surface of the wing is a row of feathers (Plate X X X . fig. b, a), bearing the same relations to the remiges as those just described ; these are the tectrices majores oi the lower surface (cf. Plate X X X . fig. b, and Plate X X X I . fig. b). If tig. b, Plate XXXII., be examined, which shows the relations of the above feathers in section, starting at the tip of the wing the remicle, or predigilal 2 (R'), is seen to have proximal to it a dorsal and ventral covert, forming a group of three. The next remex is similar, and so to the 1st metacarpal, whose dorsal covert is very small and rudimentary. These relations show that the remicle is a small metacarpo-digital which has probably not been differentiated into a flight-feather. The cubitals show the same arrangement except the fifth group, where there are a pair of coverts, but no remex; this condition is termed aquincubital, and is later described more fully. On the dorsal surface the next row of feathers to the t. majores are the median coverts (Plate X X X . fig. a, /3), or tectrices media, arranged serially with the other groups. On the cubitus they lie with a reversed overlap to the remiges and t. majores ; those, however, which lie most proximal are unreversed (S. p. 415, footnote, and Goodchild, P. Z. S. 1886, p. 191). Those on the manus lie unreversed, and generally the median covert of the 2nd metacarpal is wanting (cf. Plate XXXII. fig. 8). On the ventral surface of the wing, the next row of feathers (Plate X X X . fig. b, {3) bears similar relations; they are the tectrices media oi the lower surface, and always lie with reversed overlap to the remiges and t. majores (S. p. 491). The distal four or five are generally deficient on the manus in the Duck (Plate X X X I . fig. b). In many birds they are nearly all suppressed on the manus. The tectrices majores and mediae on the ventral surface have at first sight an anomalous position. Being on the ventral side of the adult wing, one would expect the backs of the feathers to look ventralwards, whereas they look dorsalwards just as do the remiges. This is pointed out by Sundevall (S. p. 419), who, however, gives an erroneous explanation, saying they are aftershafts developed at the ex jense of the true feather-shaft; a more probable explanation is discussed later. m The feathers so far described are seated in the wing-membrane, |
