1895.] OS THE HEAET OF THE ALLIGATOR. 347 



parietes by delicate muscular threads, which may be compared with 

 the papillary muscles of the valves of the mammaUan heart. 



In spite of the luminous investigations of Prof. Lankester upon 

 this matter, and of the previously expressed views of one of us \ 

 we cannot regard the morphological relationship of the different 

 parts of the valve of this animal and that of the bird as thoroughly 

 cleared up. 



Fig. 3. 



Heart of the Common Fowl, opened to display the cavity of the right 



ventricle. 

 X, X. Cut surfaces. 



b. Eight part of the valve identified by us with riglit part of valve in Alligator 

 (fig. 2, d). c. Septal part of valve identified by us with Alligator's 

 septal flap (fig. 2, c). a. Muscular bridge ideutified by us with structure 

 shown in fig. 2, e. 



The view taken by Prof. Lankester, and generally accepted, is 

 that the entire fleshy valve of the right (6) ventricle of the Bird's 

 heart corresponds to one half only of the complete valve of the 

 Crocodile " and of the Mammal ; in the Bird it is held that the 

 septal half of the valve is quite absent and not even represented by 

 rudiment. Now, if we consider the Bird's heart in a position exactly 

 corresponding to that of the Alligator as shown in our drawing 

 (fig. 3), this comparison seems to be inexact. The larger half of 

 the valve lies on the right side, and is of course entirely fleshy ; 

 in the Ostrich, which we have recently had an opportunity of 

 examining and which was typically avian in every respect, this half 

 of the valve was slightly sculptured on its right face near to the 

 origin from the walls of the heart. A comparison in this matter 

 with the corresponding face of the same valve in the Alligator will 



1 F. E. Beddard, " On the Heart of Apteryx," P. Z. S. 1885, p. 188, and 

 " Notes on the Anatomy of the Condor," P. Z. S. 1890, p. 142. 



^ " Bei Vogeln am rechten Ostium die mediale endocardial Taschenklappe 

 der Krokodile vollstandig geschwunden," Eose, Morph. Jahrb. 1890, p. 80. 



