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Show 588 MR. F. E. BEDDARD ON THE [Dec. 3, been dissected by me) ; and in addition one liver-lobe-the right-commonly separated from the abdomen by a thin membranous septum. In Hornbills both lobes of the liver are thus shut off; I have figured this condition in Bucorvus abyssinicus 1 ; it is exactly the same in one or two other species which I have subsequently studied. This condition is, so far as my experience goes, rare in birds ; since, however, I propose later to bring forward some facts relative to the arrangement of the viscera and the partition of the ccelom in birds, I only dwell upon this character now as tending to separate the Bucerotidae from most of their allies. Syrinx. Aceros nipalensis.-The last rings of the trachea are fused together to form a solid box, at the sides of which, however, the individual rings are recognizable. In front the last three rings are thus fused, but behind two additional rings fuse with the others to form a wide and deep bony plate. The tracheal rings lying in front of these five show the dovetailing arrangement which is so often found in the tracheal rings. The pessulus is well developed and bony, but owing to the complete fusion of the tracheal rings both posteriorly and anteriorly it is impossible to say from which rings it is developed. The intrinsic muscles of the syrinx are attached near to the boundary-line between the last and the penultimate tracheal rings. The bronchial semirings are cartilaginous, and there is a considerable interval between the first of these and the last tracheal ring. Bucorvus abyssinicus.-The syrinx of this Hornbill (fig. 1, p. 589) differs in many particulars from the last. The tracheal rings are not ossified, and there is no box formed by their fusion. Only posteriorly are the penultimate ring and the two in front of this fused just at the origin of the pessulus; anteriorly the pessulus is fused with the antepenultimate tracheal ring, which forms with it a three-way piece ; the last two tracheal rings do not meet in front. The slender syringeal muscles are attached to the anterior margin of the last tracheal ring. The peculiar shaped tracheal rings are hardly recognizable until about the 14th from the end. Buceros rhinoceros (fig. 2, p. 589) has a syrinx which is not very different from that of Aceros. The same rings are fused to form an ossified box; but the fusion between the several rings is hardly so extensive as in Aceros; furthermore the syringeal muscles are attached to the posterior border of the last tracheal ring. In Sphagolobus atratus there is very little fusion between any of the last tracheal rings ; the last three rings, which alone show any signs of ossification, are fused for a very short space anteriorly ; posteriorly there is no fusion at all, and the pessulus can be plainly 1 "Notes on tbe Visceral Anatomy of Birds.-I. On the so-called Omentum." P. Z. S. 1885, p. 842, woodcut, fig. 2, L. |
