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Show 332 DR. GADOW ON THE ANATOMY OF PTEROCLES. [Mar. 21, large group and the Fowls the other, because then this Plover- Pigeon group would include a form, viz. Pterocles, which we know to be more closely allied to the Rasores than to Charadrius. It must also be remembered that Snipes and Gulls are closely related to the Plovers ; and of course Pterocles cannot be placed in such a position as would indicate that it is more closely related to the Gulls than to the Grouse. Thus it will be best to make a group or family Pterocletes, as Mr. Sclater has done, coordinate with those of Pigeons, Plovers, Gull, Fowls, and the like. On the other hand, if we are to answer the straightforward question Is Pterocles more nearly allied through its ancestors to the Pigeons or to the Fowls? we are compelled to say that they are nearest to the Pigeons. Of course they have many features in common with the Fowls; but in no case we can include them under the latter, for the following reasons :- Pterocles shows some, although only a few, anatomical points which we only find amongst the Columbida?, whilst all the other numerous points in which it resembles the Fowls are such as must have been common to the old ancestral Stork, as we find them again in some of the Limicola?. But some of its Columbine features it is impossible to trace so far back, as they indicate a very high degree of specialization. Pterocles must have branched off from those birds which we may term " incipient Pigeons," and then, for reasons we can only suggest (perhaps similar conditions of life, and the like), have preserved and developed many of those old characters which the Fowls have also inherited from the same source, and have them developed in a similar way, as living under the same conditions. The main part of the aucestral or incipient Pigeons at the same time started in another direction, losing, as they proceeded, many of the old characters1, and acquiring numerous new ones, till they became that, highly specialized group which is now called Columba?. 1 Among the most important characters common to tbe ancestral stock which the Pigeons have lost, or are in process of losing, are the following:- 1. The Pigeons have nearly completely lost the crecal appendages of the rectum. 2. There seems to be a tendency to lose the ambiens muscle, as in many of the Pigeons it is completely absent, and in others this muscle is unstable in its presence. 3. They have lost the aftershaft to the feathers. 4. They have almost completely lost their nestling plumage, and the old character of being autophagous birds, as their young are now batched nearly nude, blind, utterly helpless, and depending entirely on their parents, and have to spend a considerable part of their childhood in a very imperfect state. |