| OCR Text |
Show 176 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, adult bird. The 2nd and 3rd have strong fused riblets, 4 millim. long, and the whole vertebra is 15 millim. across. Here is a sub-extinct type with three pairs of buttresses, or, in other words, three pairs of dorso-lumbar vertebrae, covered by the pre-ilia ; in Chauna there are eight such vertebrae. The three next have only upper transverse processes (diapophyses); these, and those of the first three are all fused together above, and also to the ilia. Fenestrae appear behind; there are four pairs of these between the upper transverse processes of the last five vertebrae, all the rest of the roof is plastered over with thin bone-an ossified " aponeurosis." The 7th sacral has a small pair of inferior bars or riblets, in my older specimens, but these are not visible in the younger; but they make very little difference to the general concavity, right and left of the fused centra; the 7th vertebra is the 1st urosacral. The 7th urosacral, or last general sacral, is the widest across its transverse processes, it is 30 millim. wide; the first of that series is only 13 millim. across. The 9th, 10th, and lith sacrals are carinate, below, the 12th and 13th recover their width, and these are not quite ankylosed together, even in the older specimen. The general concavity right and lett of the ankylosed centra, which is filled by the emerging nerves and the lobes of the kidneys, is not closed in behind, as in many birds, by rib-like thickness of the post-ilia, and special enlargement of the transverse processes of one or more of the urosacrals. Here we have the general open or unenclosed condition of the under surface, behind the " pre-iliac buttresses," that is seen in the Toucan aud the Woodpecker, a somewhat common state of things in birds with a rather short, broad, and gently convex pelvis, such as many of the Coccygomorphae possess. Unlike this state of things, we see in Corythaix and Geococcyx, as in the Raptores, a remarkable closing in of these concavities, by the special growth of post-ilia and the hinder urosacrals. Behind their middle, the series of the seven caudal vertebree (cd.v.) gradually shorten their transverse processes, which become wider as they shorten; the last free joint is 15 millim. across, the 1st is 29 millim., a little less than the width of the last sacral. A rudimentary chevron bone is seen on the 4th, and a large growth of this kind is present on the 5th, 6th, and 7th. The latter or compound bone is 24 millim. long, slender, and subfalcate, being arched somewhat on its sharp dorsal edge. The ventral edge is thick, but sharpens out behind, where the bone is somewhat lobate, and from 2*5 millim. becomes 3 millim. across in front; this bone is 7 millim. deep, it is evidently made up of 5 or 6 rudiments. Towards the end of the caudal series the procoelous joint is established once more, and in the last of these articulations the joint-cavity is as complete as in the occipito-atlantal articulation; this is a common character in arboreal birds with a large and very mobile tail. The sacral and caudal series both measure 48 millim. iu length |
