| OCR Text |
Show 274 MR. W. T. PYCRAFT ON THE [Mar. 17, The 1st lumbo-sacral shows vestiges of ventri-lateral processes. Only the 2nd sacral bears ribs. There are 8 free caudals, but the 7th is nearly fused with the pygostyle. The total number of vertebrae is 41. I must here point out that the determination of the sacral vertebra? in the skeletons herein described is a purely arbitrary one ; they cannot possibly be determined with certainty without examination of the sacral nerve-plexus, and this I am unable, at the present moment, to make. Thus, it may be that the plexus will show that in some cases what is here described as the last lumbo-sacral in reality is the first sacral. If this should be the case then, of course, the vertebra herein described as the 2nd sacral would be the 1 st caudal. v . T h e R ib s . The cervical ribs, in the Cuculi, form a series of very broad pleur-apophyseal lamellae enclosing the usual vertebra i-terial canal. These plates extend backwards rather beyond the middle of the centrum. Seen from the ventral surface, the rib is free for about half its length. Certain of the vertebrae in the middle of the cervical chain have this lamella pierced by a large fenestra. In Guira, Coua, Centropas, the 5th, 6th, and 7th are so distinguished; in Crotophaga the 6th, 7th, and 8th ; in Scythrops the 7th and 8th ; in Taccocoua, the 4th, 5th, and 6th. Cuculus, Chrysococcyx, and probably other smaller forms, differ from the forms just described in that the anterior cervical ribs are comparatively long and slender, not lamellate; whilst from the 7th vertebra backwards the ribs are reduced to vestiges. The cervico-thoracic ribs number two or three pairs. The third pair always bear uncinates. There are five pairs of thoracic ribs, though not more than four are attached to the sternum. The fifth pair are overlapped by the preacetabula.r ilium, and may be reduced to the merest vestiges, e. g. Rhamphococcyx and Coua, or they may be complete, as in Scythrops and Cuculus. They vary somewhat in form. For instance, in Coua, Centropus, and Guira the proximal end of the rib is extremely broad, and the shaft after leaving the vertebra almost at right angles, curves abruptly downwards. In other Cuckoos the broadening of the shaft is not conspicuous, and the shaft slopes gently downwards and backwards, so that the thorax is conspicuously broader at the articulation with the sternal ribs than above. The uncinates are broad and strong, and show a tendency to develop a sharply defined postero-inferior angle at the junction with the shaft of the rib ; this is especially noticeable in Coua. The sternal segments of the 5th pair of thoracic ribs never reach the sternum. They may persist as vestiges, even the thoracic segment of the rib reaching the verge of disappearance, as in Coua and Rhamphococcyx, or they may be of considerable size, |
