1882.] OF ORNITHORHYNCHtIS PARADOXUS. 559 



Fig. 9. Eight aiiriculo-ventricular valve of Phalangisfa. a, h, anterior 

 musculi papillares. 



10. Ditto of Phascoloynys. Letters as before. 



11. Ditto of Mtts. Letters as before. 



Plate XL. 



Fig. 12. Ornitiioi!iiynciius No. 1. Eight ventricle opened and its anterior 

 wall reflected so as to expose the valve. 



a, great or anterior muscular column (musculus papillaris) ; b, 

 right muscular column (musculus papillaris); c, left or " conus " 

 muscular column ; P. A, orifice of pulmonary artery ; B. A, right 

 auricle ; R. V. C. S, right vena cava superior ; A, aorta. 



13. Ornithorhynchus No. 2. Similar dissection of a second speci- 

 men. 



a, great or anterior muscular column ; h, b, b, the three slips which 

 represent the single column b of specimen No. 1 ; m, n, two additional 

 nuiscular columns in the same region, which do not traverse the mem- 

 branous part of the valve, but pass from the centre of the right mus- 

 cular arch to the anterior wall of the ventricle, from connexion with 

 which they have been cut, leaving the bases m',n'; x,y. " columnce 

 carnese " connecting the base of the great muscidar column with the 

 anterior ventricidar wall ; x', y', the cut bases of the same ; e, left 

 muscular column ; P. A, orifice of pulmonary artery. 



14. Ornithoeuynchus No. 1. The great anterior column cut and the 

 valve reflected. Letters as in fig. 12. 



15. Ornithorhynchus No. 1. Both the great 'and the right muscular 

 columns are cut. Compare with the human heart, fig. 2. 



Letters as in fig. 12, except lac, left anterior portion of the mem- 

 brane of the valve ; rac, right anterior portion of ditto ; ^j c, pos- 

 terior or septal portion of ditto. 



16. Ornithorhynchus No. 2. The second heart (that of fig. 13) with its 

 muscular columns cut and the valve reflected. 



«, base of the great muscidar coliunn ; «', its cut and reflected 

 ostial portion ; b, b, bases of two of the right small muscular columns ; 

 b', b\ their cut ostial portions ; e, left muscular column ; lac, left 

 anterior portion of the membrane of the valve ; rac right anterior 

 portion of ditto ; ^^ c, the very minute posterior or septal rudiment of 

 ditto. 



17. View of the left auriciJo-venlricular valve of OrnithorhyncJws. The 

 apes of the ventricle has been cut away ; and the observer is supposed 

 to look upwards towards the aortic and auricular orifices, ebd, three 

 muscular columns (papillary muscles) giving attachment to the valve ; 

 cor, corpuscles resembling the corpuscula Arantii, at the central point 

 of the margin of each flap of the triradiate valve ; L. A, left aui-icle ; 

 Ao, aortic orifice. 



Plate XLI. 



Fig. IS. Eight auriculo-veutricular valve of Didel^phys. a, equivalent of the 

 great anterior papillary muscle of Man ; b, equivalents of the right 

 anterior papillary muscle of Man. 



19. Ditto of Phascohrctos. 



20. Ditto of Myrmeco]phaga. c, as in fig. 1. 



21. Ditto of Erinaceus. 



22. Ditto of Cmcus. 



