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Show 1889.] MR. W. K. PARKER ON STEATORNIS CARIPENSIS. 175 seen how Bucerine the palate is. This isomorphism, however, has to be taken for what it is worth ; it is very limited, and in the great Cuculine group (Coccygomorphae) we everywhere meet with characters in one Family that correspond in some degree with those in another, where everything else is very unlike. This is to be noted in the contrast seen between the dorsal vertebrae of the Bucerotidae and those of Steatornis. In the former they are cylindroidal, and very broad, widened, andflat below; those of the latter run into a mere keel. Also, in the Bucerotidae the spines in the dorsals form a feeble saddle-backed series, having a concave general outline ; in Steatornis they form a strong straight series, and the interspaces between the spines are very small. In a New-World Kingfisher (Ceryle alcyon) the hinder dorsal centra make a great approach to those of Steatornis, without, however, being opisthoccelous. The peculiarity just referred to in the ribs is their great breadth above, their narrowness below, and the low position of the uncinate processes (p.u.). The second pair are the widest; they are 6 millim. across for some distance below the tuberculum, and only 3 millim. near the lower condyle ; the processus uncinatus is only 11*5 millim. at its base, above that, the condyle is 13 millim. long, and has an average breadth of 2*5 millim. The 1st sacral has a pair of ribs which have a sternal piece, imperfect, but 17 millim. long. The 1st dorsal sternal piece is 14 millim., the last 28 millim. long ; they have an average width of 2 millim. The sacral vertebree and the whole pelvis (Plate XIX. figs. 2, 3, and Plate X X . fig. 6) are very much like those of Ceryle alcyon,-the Kingfisher whose dorsals show a tendency to the opisthoccelous character, and have deep, concave-sided dorsal centra, with long, basally-dilated, inferior spines. As in that bird and the Hornbills the sacrum is completely ankylosed to the iliac bones, even in the young bird of the first year. This perfect union of the lateral with the median elements of the pelvis is seen in the Common Cuckoo (Cuculus canorus) in young birds of the first summer, but it is not seen in Coccyzus nor in Saurothera, even in old birds, so that this character must be a thing dependent upon conditions, being so variable in nearly related types. The most remarkable thing of all, however, is this, namely, that whilst these parts are completely ankylosed in the young Cuckoo, in the hinder half of the sacrum of an old bird the sutures are quite distinct. This is a phenomenon of the same nature as the re-segmentation in the adult of the last sacral of the young bird to increase the number of the free caudal vertebrae, a very common thing in the higher birds 1. The first three sacrals are not yet ankylosed by their centra in the youngest specimen, and the 1st only is partly distinct in an 1 I cannot leave this part of m y description without remarking that this must be part of some general law with regard to the evolution of the higher kinds of birds. Intense ossification is the thing we are most familiar with in the osteology of birds, as compared with other Vertebrata. And yet the birds that are manifestly most archaic are often most intensely ossified : thus, to take a single fact, an archaic bird is often, not always, desmognathous, whilst a more specialized, newer, and nobler bird of the same family will be schizognathous. |
