256 MR. W. P. PYCRAFT ON THE MORPHOLOGY AND 
d. THE Cuoana (Pl. XLV. fig. 1). 
The choane of the Palwognathe, it is interesting to remark, differ in form from the 
Neognathe in their larger size. In all the Neognathe the aperture is slit-like, whilst, 
as will be seen in the figure, in the Palwognathe it is triangular or cordiform in 
shape. 
CIRCULATORY SYSTEM. 
Tue Heart. 
The heart of the Palwognathe does not differ materially in structure from that of 
the Neognathe. It has been already ably described and its most important features 
pointed out by Owen [67], Lankester [45, 46], Beddard [5], Rolleston [87], and others, 
so that little remains for me to say. 
Fig. 8. 
B. 
A. ace... Sp. Uv: 
A.—Dissection of the heart of Casuarius unappendculatus, to show the right auriculo-ventricular valve and 
the “‘ moderator band.” 
B.—--Dissection of the heart of Rhea americana, to show the right auriculo-ventricular band and the abnormal 
septal valve. 
acc.t. = accessory tendon. 
sep.v. = septal portion of right auriculo-ventricular valve. 
s.v, = semilunar valves. 
r.au.v. = right auriculo-ventricular valve. 
p- = papillary muscle. 
mod.b, = moderator band. 
