256 



ME. W. P. PYCEAFT ON THE MOEPHOLOGY AND 



d. The Choam (PI. XLV. fig. 1). 

 The choanse of the Pakeognathce, it is interesting to remark, differ in form from the 

 Neognathce in their larger size. In all the Neognatlue the aperture is slit-like, whilst, 

 as will be seen in the figure, in the Pakeognathce it is triangular or cordiform in 

 shape. 



CIECULATORY SYSTEM. 



The Heart. 



The heart of the Palceognathce does not differ materially in structure from that of 

 the Neognathce. It has been already ably described and its most important features 

 pointed out by Owen [67], Lankester [45, 46], Beddard [5], Eolleston [87], and others, 

 so that little remains for me to say. 



Pig. 8. 



r. uu. -it 



sefo.th 



xt&ct 



77ia<£ & 



KCOZiV: 



A. — Dissection of the heart of Casuarius unapjpendmlatus, 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. 



ae2).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. 



