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Show 320 PROF. D'ARCY W. THOMPSON ON THE [Apr. 2, in the main the two tracts are separated by a prolongation backward of the triangular apterion at the base of the neck. The pollex is entirely concealed beneath the skin and bears no free alula, though a few somewhat larger feathers appearing among the marginals correspond to the position of the latter. The whole wing is of a remarkably simple type. The small number of marginals, the scanty feathering of the patagium, and the absence of minor coverts on the whole dorsal and greater part of the ventral surface of the wing seem to m e to leave the arrangement of the remaining rows unusually clear; and in particular, the relation of the upper and lower posterior extensions, parapteral and hypopteral, of the coverts to the rows of coverts themselves seems to be much more simple aud definite than is usual. The wing of Collocalia has ten primary feathers and seven well-developed secondaries, internal to which latter are two rudimentary ones. There is a greater covert to each of the primaries on the dorsal side and another on the ventral, of which, if m y interpretation be correct (for it is in part subject to the same difficulty that I have discussed in describing Patagona), the ventrals are all proximal to, and the dorsals distal to, their corresponding primaries. There seem here to be clearly intercalated at the wrist a pair of dorsal and ventral carpal coverts. There is no aquincubital covert among the secondaries, at least in this particular Swift; there are seven major coverts on the ventral side, and on the dorsal side the series is further prolonged backwards to connect with the humeral tract. On the dorsal side of the wing there are median coverts present in connection with the seven outer primaries and all the secondaries, which latter are furnished also with a row of minor coverts. Median coverts are present on the ventral side in connection with all the primaries and secondaries, aud are further continued backwards into a line of hypopteral feathers. O n the ventral side of the manus is an incomplete row of minor coverts. The marginals are few, but the patagium bears on the dorsal surface more numerous feathers (in 3 or 4 rows) than in the Humming-bird. The wing of Caprimulgus macrurus (text-fig. 82, p. 321) possesses ten primaries and ten conspicuous, together with one or two rudimentary, secondaries. There is a rudimentary remex at the carpal joint. The alula is of large size aud bears three long feathers. O n the dorsal side of the wing there is a major covert corresponding to each primary, to each secondary including the rudimentary carpal remex, and also a well-marked ' aquiutocubital' feather. The six outer primaries (that is to say, numbers 5 to 10) possess each a well-formed median covert, and the first and second also each possess two coverts, the outer (or that corresponding to the median covert) being of large size, though not so big as the major one; besides these, the dorsal surface of the hand possesses no other coverts. The secondaries all possess well-formed median as well as major coverts, iucludingone tor the aquiutocubital feather; and these are succeeded by three rows of minor coverts, which rows become |
