. On the natural history and classification of birds . of trees :all these feathers are lan-ceolate, that is, terminat-ing gradually in a point ;the webs diminishing inbreadth as they approachthe extremity, but whichis never naked ; most ofthem, also, have the webs on both sides nearly next modification is seen in the family of Cer-thiadce or creepers, but more especially in the Braziliangenus Dendrocolaptes; here we find the external shaftvery narrow, while the internal is remarkably broad ;both, however, terminate before reaching the extremityof the feather ; so that about a quarte
. On the natural history and classification of birds . of trees :all these feathers are lan-ceolate, that is, terminat-ing gradually in a point ;the webs diminishing inbreadth as they approachthe extremity, but whichis never naked ; most ofthem, also, have the webs on both sides nearly next modification is seen in the family of Cer-thiadce or creepers, but more especially in the Braziliangenus Dendrocolaptes; here we find the external shaftvery narrow, while the internal is remarkably broad ;both, however, terminate before reaching the extremityof the feather ; so that about a quarter of an inch of theshaft, at its tip, is entirely naked, and the tip itselfacutely pointed and inclined downward. This structurewill be perfectly understood by the annexed figure (b),while the the abrupt manner in which the broad innershaft terminates is better seen in the genus Oxyurus.{fig. 56. a.) Now it is quite clear, that a tail thusconstructed has equal, if not greater power than that ofthe woodpecker in assisting a bird to climb, inasmuch as. 108 ON THE CLASSIFICATION OF BIRDS. these horny points will enter into crevices and inequali-ties of the bark, which the more thickened tips ofthe woodpeckers quills would glide over. A thirdmodification is seen in the tail of our common creeper(Certhia familiaris), where the form of the feathers isunequally lanceolate (fig. 55. e); that is to say, they gra-dually taper to a point; but the inner web is near fourtimes the breadth of the outer, the webs themselvesbeing continued to the very tip of each feather: theshaft also is neither enlarged, or is it near so rigid, as inthe preceding group. The next variation of the scan-sorial structure is peculiar to the Brazilian genus Sclerurus(fig. 56. d) and the Australian genus Orthonix (c); twoforms, inhabiting different regions, but which are unques-
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Keywords: ., bookcentury1800, bookidonnaturalh, booksubjectbirds, bookyear1836
