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Show 450 MR. A. H. GARROD ON THE [May i 5, colaptes albicollis, Picolaptes affinis, Thamnophilus murinus, Thamnophilus doliatus, Thamnomanes glaucus, Grallaria guatemalensis, Hylactes megapodius, Pteroptochus albicollis, or any other Passerine bird with which I am acquainted. They are, in fact, schizorhinal, like the Charadriiformes ; in other words, the osseous external nares are in the form of triangular openings, the apical angle of each of the triangles being situated between the inner and outer process of the nasal bone of the corresponding side1. Figure 3 gives a view of the Superior surface of skull of Furnarius rufus, to show the schizorhinal form. upper surface of tbe skull of Furnarius rufus. It has been my habit to group all the birds possessing the schizorhinal skull in a single major division, including the restricted Limicolae, the Gruidse, Laridse, Alcidse, and the Columbidse ; but the independent development of an identical disposition in the small division of the Passerine birds above mentioned weakens the importance of the character to a certain extent, although it is not at all necessary to assume that it overthrows its significance. Collateral evidence, from visceral and other details, compels me still to think that those schizorhinal birds which possess the ambiens muscle-or are, in other words, homalo-gonatous2- must be retained in one great order, the Charadriiformes, until some important structural differences are discovered which necessitate their being otherwise arranged. The schizorhinal disposition is most certainly one which is a secondary development upon the normal holorhinal nares ; and that it has been independently arrived at in two non-related orders of the class is proof that it results from most simple causes, because the probability that the same complex conformation should appear de novo varies inversely as the complexity : the greater the elaborateness the less the chance that it, in all its detail, comes into existence more than once. A still more simple variation is found in the number of the carotid arteries, the normal two being reduced to the left only in certain members of 1 Vide P. Z. S. 1873, p. 33. 2 Vide P. Z. S. 1874, p. 116, |