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Show 174 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, small spine that looks forwards; this structure is seen, but not so well, in the 6th and 7th, and then dies out. The 6th is the longest of the series ; it is 13*3 millim. long, and 11 millim. wide, over the pre-zygapophysis. The 9th and 10th have oval knobs on their post-zygapophyses. The upper spine begins again on the 12th, on the 14th it is oblong and large like those of the dorsals, but smaller; in the 15th it is three fourths the size of those on the dorsals. The last six cervicals have a small inferior spine ; this is trifid in the 14th, and is dilated into a broad plate in the last. The 13th has a small, free, V"shaPed rib ; in the 14th the left rib is very slender, but it is 22 millim. long, whilst its right rib is only 7 millim. long. On the right side the 12th has a V" shaped, distinct rib. The last cervical only differs from a dorsal in having no sternal piece; it bas the uncinate process or bone (this is a distinct element), and is nearly as long in the 1st dorsal. The posterior part of this 15th vertebra is intermediate in character between cylindroidal and opisthoccelous. M y memory fails me in endeavouring to think of any other existing bird with more than three distinct ribs in the cervical region, even on one side ; there is often a want of symmetry in this part of the spine, as well as in other parts, e.g., atlas, sacrals, &c. This fact-that, at least on one side, four ribs remain free in the lower part of the neck- coupled with what I shall now show as to the structure of the dorsal vertebrae, gives me tbe right to say that this is a very archaic or quasi-reptilian type. The four dorsal vertebrae have very long and sharp upper spines, and the first two have, also, simple lower spines; the dilated plate seen in the last cervical has died out, and the process itself greatly elongated, downwards. The front face of the 1st dorsal centrum is cylindroidal, the rest of the articulations of the dorsals and the last dorsal with the 1st sacral is opisthoccelous. The centra are narrow, almost Chelonian in this respect, the 1st and 2nd are mere keels. The posterior cup of each dorsal centrum is well excavated, and there is, right and left, at its upper part, a pair of semi-oval enlargements of this facet, that look like an additional pair of sygapophyses ; hence, on the side view, the outline of the hollow end of each centrum is deeply notched at its upper third. Each of these secondary facets has its own concavity, so that each centrum fits to the one behind it by three hollow facets, one large, below, and two small, above ; the articular cartilage is very thick in these vertebrae. Thus, although this mode of articulation is archaic, it is also intensely specialized by this modification (Plate XVIII. figs. 5, 6). Up to the present, this is the only Cuculine type, except the Psit-tacidee, in which I have found the dorsals to be opisthoccelous. It is common among Water' and Wading birds. The ribs (Plate XIX. fig. 1) are very peculiar; they resemble those of the Hornbills, but the peculiarity seen in those birds is exaggerated in this. This is worth considering, as we have just 1 The secondary facets just described are not so distinct in Parrots and Plovers as in Steatornis, which is equal to Chionis in this respect. |