4S0 PROF. LANKESTER ON THE HEART OF APTERYX. [May 5, 



Fig. .5. 



Heart of Onnthorhync'hus. 

 The right, Tentricle opened so as to expose the right cardiac valve. There is no 

 connection here of the great anterior muscuLir band («) of the valve 

 with the free wall of the ventricle. It arises entirely from the septal 

 wall. The distinction is not a fundamental one ; the muscular band a 

 in figs. 5 and 6 is to be identified with the muscular band a of the Birds' 

 hearts (figs. 1 to 4). Similarly the much shorter muscular band or fold 

 c in the Birds' hearts appears to be the same structure as the band 

 marked c in the present figure of the right cardiac valve of Oniitho- 

 rhynchus. 



Fig. 6. 



-P'- 



The same heart as that drawn in fig. 6, with the great anterior muscular band 

 {a) cut through, so as to allow the valve to be reflected, for comparison 

 with the similar views of the heart of the Fowl, fig. 2, and the heart of 

 Apteryx, fig. 4. 



Letters in all the figures. 

 a. The large anterior muscular band passing from the free margin of the valvular 

 flap to the ventricular wall (this is the great anterior muscuhis papil- 

 laris of M.ammals). h. The muscular flap of the Birds' valve, c. The small 

 left muscular band of attachment from the valve to the ventricular wall 

 (lelt or " conus '' musculus papillaris of the Mammal). 



