. The structure and classification of birds . es of Ichthyornis to Hesperornis have beendwelt upon by some; but it appears that Ltdekkbesremark, that the Odontornithes are a series of birds ances-tral to the modern series of toothless carinates, expresses thetruth. He has furthermore added that this series differsfrom the Euornithes (Stejnegers name for carinates) by theabsence of union between the rami of the mandible andbetween the distal ends of the ischium and ilium, likenesseswhich do not mean a near rela/tionship, but express thedegree of development of bird structure at that period. 472
. The structure and classification of birds . es of Ichthyornis to Hesperornis have beendwelt upon by some; but it appears that Ltdekkbesremark, that the Odontornithes are a series of birds ances-tral to the modern series of toothless carinates, expresses thetruth. He has furthermore added that this series differsfrom the Euornithes (Stejnegers name for carinates) by theabsence of union between the rami of the mandible andbetween the distal ends of the ischium and ilium, likenesseswhich do not mean a near rela/tionship, but express thedegree of development of bird structure at that period. 472 STRUCTURE AND CLASSmCATION OF BIRDS ACCIPITRES Definition.—Aquinoubital. Oil gland present. Two carotids. Skulldesmognathous and holorhinal. Cseca rudimentary or present. Biceps slip absent. This large group of birds admits of but a scanty defini-tion, if we are to include in it, as is here done, the secretarybird and the American vultures; for it then shows a con-siderable amount of structural variation. The^oil gland, Ana. Fig. 226.—Tensobes Patagh of Polyboroides (after Beddaed)., tensor patagii longus; ^ tensor brevis; Anc^ anconeeus ; By deltoid. invariably present, is generally feathered, but nude in theCathartidse. In Serpentarius this gland varies in size; inone specimen it was found to be very small and to have avery minute tuft. The after shaft is absent in the Cathartidse and in Pandion,present in other Accipitres. Twelve rectrices is the usual ACCIPITRES 473 number, but fourteen occur in Neophron percnopterus andBhinogryphus californianus. There are potoder-down patches in Elanus, Circus, andGypaetus. The pterylosts is described for a variety of typesby NiTZSCH. The ventral tract broadens out on the breast, whereit is even sometimes (Gyps fulvus) divided into an outerand inner branch. The dorsal tract forks upon theshoulders; in Gypaetus barbatus each limb of the fork isconnected by a single rov? of. feathers with the long singlemedian
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbirds, bookyear1898
