588 MR. F. E. BEDDARD ON THE [DeC. 3, 



been dissected by me) ; and in addition one liver-lobe — the right — is 

 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 ' ; it is exactly 

 the same in one or two other species which 1 liave 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 Bucerotidse 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 de- 

 veloped. 



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 consider- 

 able interval between the first of these and the last tracheal ring. 



Bucorvus ahjssinicus. — 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 Sphagolohus atratus there is very little I'usion 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 the Visceral Anatomy of Birds. — I. Ontbe so-called Omentum." 

 P. Z. S. 1885, p. 842, woodcut, fig. 2, L. 



