1882. | OF ORNITHORHYNCHUS PARADOXUS. 909 
Fig. 9. Right auriculo-ventricular valve of Phalangista. «a, b, anterior 
musculi papillares. 
10. Ditto of Phascolomys. Letters as before. 
11. Ditto of Mus. Letters as before. 
Puate XL, 
Fig. 12, Ornrrnornyncnus No. 1. Right ventricle opened and its anterior 
wall reflected so as to expose the valve. 
a, great, or anterior muscular column (musculus papillaris); 6, 
right muscular column (musculus papillaris); e, left or ‘conus ” 
muscular column; P. 4, orifice of pulmonary artery; R. A, right 
auricle; &. V. C. 8, right vena cava superior; A, aorta. 
13. Ornrrnornyncnus No. 2, Similar dissection of a second speci- 
men. 
a, great or anterior muscular column; 3, 6, d, the three slips which 
represent the single column 2 of specimen No. 1 ; m, 7, two additional 
muscular 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, ‘column 
carnese” connecting the base of the great muscular column with the 
anterior ventricular wall; 2', 7’, the cut bases of the same; e, left 
muscular column; P. A, orifice of pulmonary artery. 
14, OrnitHoruyncuus No.1. The great anterior column cut and the 
valve reflected. Letters as in fig. 12. 
15. OrnitHoruyncnus 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 Jac, left anterior portion of the mem- 
brane of the valve; vac, right anterior portion of ditto; pc, pos- 
terior or septal portion of ditto. 
16. OrnitHoruyncuus No. 2. The second heart (that of fig. 13) with its 
muscular columns cut and the valve reflected. 
a, base of the great muscular column; a’, its cut and reflected 
ostial portion ; %,, bases of two of the right small muscular columns ; 
b', b', their cut ostial portions; @, left muscular column; / ae, left 
anterior portion of the membrane of the valve; rac right anterior 
portion of ditto; pe, the very minute posterior or septal rudiment of 
ditto. 
17. View of the left auriculo-veniricular valve of Ornithorhynchus. The 
apex of the ventricle has been cut away ; and the observer is supposed 
to look upwards towards the aortic and auricular orifices. ed, 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; JZ. A, left auricle ; 
Ao, aortic orifice. 
Prats XLI. 
Fig, 18. Right auriculo-yentricular valve of Didelphys. a, equivalent of the 
great anterior papillary muscle of Man; 4, equivalents of the right 
anterior papillary muscle of Man. 
19. Ditto of Phascolarctos. 
20. Ditto of Myrmecophaga, ¢, as in fig. 1, 
21. Ditto of Hrinaceus. 
22. Ditto of Cuscus. 
