lb8;).J MR, F. 10. BEDDARD ON THE IIKART OF APTFRYX. 189 



of a number of closely united fleshy columns. Just before the 

 junction of the left half of the valve with the muscular flap already 

 described two minute chordae tendinece connect it with the free wall 

 of the ventricle between the attachments of the left half of the valve 

 and the free muscular flap ; the two are fused almost immediately 

 after their origin, and form a single excessively small fibrous band 

 which is attached to a papillary muscle. 



I can find no trace of the chordtE tendinecB that Sir R. Owen figures 

 arising from the lower margin of the valve and inserted towards the 

 hinder end of the ventricular cavity ; the oidy structure at all similar 

 is the slender fibrous band which I have described as conneclin" 

 the valve with the free wall of the ventricle ; this structure does not 

 appear to me to be the same for reasons which I shall put forward 

 in describing the heart of Apteryx oweni. With regard to the valve 

 itself, it is not in my specimen " in some parts semitransparent and 

 nearly membranous ;" the thickness of tlie valve, which, except for 

 a small portion on the left half is entirely muscular, is by no means 

 less than that of any otlier bird with which I have had the oppor- 

 tunity of comparing it ; the very slight development of membrane 

 on the left half of the valve close to its origin is clearly a matter 

 of no importance, since I have found this same feature to be more 

 marked in Eupodotis and in other birds. In short, my heart of 

 Apteryx, as well as a specimen in the possession of Prof. Lankester, 

 which he kindly allowed me to inspect, and another preserved in the 

 Oxford Museum, present no differences of any importance from 

 the hearts of other birds. 



Of the heart of Apteryx oweni 1 have been able to examine two 

 examples, in both of which the right auriculo-ventricular valve has 

 much the same structure. It only differs from that oi A. australis 

 in the presence of a stout muscular band arising from the septal wall 

 of the ventricle and attached to its free wall close to the fleshy bridge 

 which unites the free margin of the valve to the ventricular wall ; it 

 gives off a short branch to the latter. This structure closely cor- 

 responds to the " moderator band " described by Prof. Rolleston in 

 the heart of the Cassowary ; the chordte tendinecB which I have de- 

 scribed ill the heart of A. australis probably represent the upper 

 portion of the moderator band of A. oiveni. 



I have examined a large series of hearts of birds with a view to 

 discovering if there were any deviations from the normal type in the 

 right auriculo-ventricular valve, but I can find none ; the only diffe- 

 rences at all are in the left-hand portion of the valve, which is more or 

 less membranous, and in a specimen of Eupodotis australis appears 

 to be entirely so. Gegenbaur, however, speaks of a rudimentary 

 septal flap in Sarcorhamplms \ 



1 Jen. Zeitschr. Bd. ii. p. 380. 



