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Show 1868.J PROF. HUAXXKY O N T H E A L E C T O R O M O R P H / E . 295 author is, in fact, a perfect mine of information for those who do not mind the trouble of digging, and I shall frequently have to express m y concurrence with the views therein expressed. But, in attempting to discover the affinities of Opisthocomus, I have been led to believe that a good deal yet remains to be done in the way of defining the limits of the Alectoromorphce, the value of the subdivisions of the group, and the relation of these subdivisions to zoogeography. I propose to make a contribution towards these objects in the present paper by discussing:-1st, the proper limits of the group Alectoromorphce and of its subdivisions ; 2ndly, the relations of sundry outlying forms, commonly regarded as Gallinaceous birds, with the Alectoromorphce and adjacent groups; 3rdly, the geographical distribution of the Alectoromorphce in relation to geographical distribution generally. I. The proper limits of the Group Alectoromorphse and of its subdivisions. In my paper "On the Classification of Birds"* I have included the Pteroclidce and the Turnicidee with the Phasianidce, Megapodidee, and Cracidee in one division, Alectoromorphce, though the aberrant characters of the Turnicidee and Pteroclidce are fully recognized. I am now convinced that it will be much more convenient to restrict the title of Alectoromorphce to the three latter groups, which agree with one another, and differ from the other two in the following osteological characters :- 1. The last cervical vertebra and the anterior dorsals are always ankylosed together in the adult. One of the posterior dorsals (generally, if not always, the penultimate) remains free, while the hindermost becomes ankylosed with the lumbar vertebrae to form part of the so-called " sacrum." 2. The number of the prsesacral vertebrae in the different regions of the body is very constantly, if not always, 16 cervical, 5 dorsal, and 3 lumbar. The total number of these vertebrae is therefore 24, or the same as in Man. 3. The maxillo-palatines vary greatly in form and size, and in the degree to which they are ossified, but they are always lamellar or conchoidal. They unite in the middle line with an ossified septum only in some Cracidee. 4. There are oval, sessile basipterygoid facets, situated far forwards upon the rostrum of the sphenoid. 5. The palatines are long and narrow, with obsolete internal laminae and rounded-off postero-external angles. 6. The angle of the mandible is produced and recurved, and the oral margins of the rami are not flanged out. 7. The external xiphoid processes of the sternum (which are much shorter than the internal ones) are bent outwards over the hinder ribs and have expanded ends. * Proc. Zool. Soc. 1867, p. 415. |