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Show 1885.] TROCHILID.E, CAPRIMULGID.E, AND CYPSELID^E. 901 this aspect of the pelvis, which strikes one upon the first glance the bone. Two more ribs follow the pair borne by the 19th vertebra • the first of these meet the last pair of costal ribs* below, while above' their tubercula and capitula have been so far absorbed that these ribs look as if they were anchylosed to the outer margin of the ilium on either side. The last pair of ribs neither meet the sternum below nor the pelvis above, but are attached to the pair just described. these nhs differ from the preceding ones in not developing epipleural appendages. This arrangement, it will be seen, gives 8 pairs of ribs • the first two pairs do not reach the sternum ; the next 5 pairs do' meeting 5 pairs of costal ribs; finally the last pair are in every sense floating ribs. Through the 27th vertebra, the following segments are appropriated by the sacrum; then come 5 free caudals, making 32 vertebra? in the spinal column of this Humming-bird, the whole being finished off by a comparatively large pygostyle, probably composed of several others. The pygostyle is terminated in a peg-like point, and is not flattened and quadrilateral as in the Swifts and many Passeres. Trochilus has a short and broad pelvis, being much compressed from above downwards. Viewed from above, we find that the open "lleo-neural grooves" are over the 18th and 19th vertebra?, the two described above as ankylosing with the fore part of the sacrum Tins arrangement is rare among existing birds-unique so far as I can recall at the present writing. The anterior and in-turned extremities of the ilia are rounded points, meeting the outer sacral margins just opposite the posterior endings of the ilio-neural grooves. The parial foramina among the diapophysesof the urosacral vertebrae are quite large. Professor Owen found them small in a specimen of Trochilus pella1. Upon a lateral view we observe that the narrow ilium is much concaved immediately anterior to the cotyloid cavity ; its outer margin forming a part of the long gentle curve completed by the postpubis which latter projects far behind where it is turned upwards. No propubis is developed. The acetabulum, ischiac, and obturator foramina'present nothing of marked interest; they have all an average size and are in due proportion with the surrounding parts. The obturator foramen is thoroughly closed in by the ischium, after which this bone arches over an obturator space, to meet the postpubis again in a little foot-like process. In many birds a notch on the hinder border of the pelvis denotes the landmark between ilium and ischium in this situation. No such feature exists in Trochilus, this Humming-bird having in the posterior portion of its pelvis much to remind us of similar parts of the skeleton in the Passeres. The sternum (figs. 3 and 6, Plate LX.).-So far as its general form and characteristics go, the sternum in the Hummers has lono- been known to us, and this information has been principally derived from 1 ' Anat. and Phys. of Vert' vol. ii. p. 32. Loud. 1866. |