. La structure et la classification des oiseaux . tellement aslatrans très asymétrique (aftee est parfois le cas; ils parfois surgissent plus nettement du côté droit de thetrachea. Les muscles intrinsèques sont toujours présents, et généralement attachés, comme le montre la figure, à la membrane entre les anneaux trachéaux avant-fin et avant-fin.ils sont parfois poursuivis un peu plus loin par ligamentoustissue. Les trois derniers anneaux trachéaux sont unis par des pièces médianbones ou cartilagineuses. Postériorly les anneaux trachéaux sont faibles, ou même défectueux dans la ligne médiane. Il s'agit du caractère général
1093 x 2287 px | 18,5 x 38,7 cm | 7,3 x 15,2 inches | 150dpi
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. The structure and classification of birds . so highly asymmetrical aslatrans (aftee is sometimes the case; they occasionallyarise more markedly from the right side of thetrachea. The intrinsic muscles are always present, andgenerally attached, as shown in the figure, to the membranebetween the penultimate and antepenultimate tracheal rings.They are sometimes continued a little further by ligamentoustissue. The last three tracheal rings are united by medianbony or cartilaginous pieces. Posteriorly the tracheal ringsare weak, or even defective in the middle line. These arethe general characters of the windpipe and syrinx in theColumbae. A few of the genera which show some slightdivergencies may now be mentioned. In Caloenas nicoharicathe intrinsic muscles are continued by ligament as far as thepenultimate tracheal ring; the first four or five bronchialsemi-rings are connected posteriorly by a cartilaginous bar, which borders the membrana tympaniformis and is continuedup as far as the sixth tracheal ring from the end of theseries.. COLUMB^ 311 In Goura there is no union posteriorly between succes-sive tracheal rings, and the last two or three are quite dis-continuous in the middle line posteriorly. In Didunculus also the last few tracheal rings do notmeet in the middle line posteriorly. As to the skull, the pigeons are schizognathous birds witha slender vomer and basipterygoid processes, absent only inDidus. They are also schizorhinal, but Goura, like Cursorius, &c., among the Charadrii, is pseudo-holorhinal. The lacrymalfuses below with the ectethmoid, and, indeed, forms with ita nearly solid and often rather massive plate of bone. InGoura, at any rate, the descending process of the lacrymalis perforated in front by a largish foramen, as in the Bhea.Some pigeons—^e.g. LopholcBmus—have amedian small circularforamen above the foramen magnum; in Macropygia, &c., this becomes a notch upon the upper border of the foramenmagnum. In Goura the foramen is totally absent. Th
