256 



ME. W. P. PYCRAFT ON THE MORPHOLOGY AND 



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



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

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

 as Avill be seen in the figure, in the PakeognathiV it is triangular or cordiform in 

 shape. 



CIRCULATORY SYSTEM. 



The Heart. 



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



the Neognatho:;. 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. 



A. 



P 



^.se;. 



fj.Z^. 



7HO<l 6 



/:c/u. it, 



A. Dissection of the heart of Casuariiis unappendciihivs, to show the right auriculo-ventricuhir valve and 



the " moderator baud.'" 



]<. Dissection of the heart of Ulna amer'mtna, to show the right auriculo-ventricular band and the abnormal 



septal valve. 



acc.t. = accessory tendon. 



sep.v. = septal portion of right auriculo-ventriculnr valve. 



s.v. = semilunar valves. 

 r.au.v. — right auriculo-ventricular valve. 



2). = papillary muscle. 

 rnorl.h. = moderator band. 



