OF THE ORNITHORHYNCHUS PLATYPUS. 
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Fig. 4. Transverse section through Duckbill’s cochlea (apex), from No. 13 of series. 
X 22 diameters. 
1. Scala tympani. 
2. Scala vestibuli. 
3. Scala media or ductus cochleae. 
4. Lamina ossea, (a) ganglion. 
5. Ligamentum cochleae, (b) stria vascularis. 
6. Membrane of Reissner. 
7. Membrana basilaris. 
8. Cavity of lagena. 
Fig. 5. Transverse section through lagena of Duckbill’s cochlea, from No. 13 of series. 
X 100 diameters. 
1. Cavity of lagena. 
2. Scala vestibuli. 
3. Nerve epithelium. 
4. Nerve fibres. 
5. Mucoid mass. 
Fig. 6. Transverse section of organ of Corti of Duckbill, built up from several 
specimens. X 400 diameters. 
1. Scala tympani. 
2 Scala media or ductus cochleae. 
3. Lamina ossea, (a) nerve. 
4. Membrana basilaris, (6) blood-vessels, corresponding to vas spirale. 
5. Triangular tunnel. 
6. Marginal sulcus. * 
7. Outer rod of Corti. 
8. Inner rod, (c) trabeculae. 
9. Inner hair cells. 
10. Outer hair cell. 
11. Cells of Deiters. 
12. Extra row of hair cells. 
Fig. 7. Transverse section of lamina ossea (Duckbill) showing a blood-vessel passing 
up on to the membrane of Reissner. X 150 diameters. 
1. Limbus of lamina ossea. 
2. Membrane of Reissner. 
3. Blood-vessel. 
4. Blood-vessel forming a knot. 
Fig. 8. Transverse section through middle of the Magpie’s cochlea. X 75 diameters. 
1. Scala tympani. 
2. Ductus cochleae. 
3. Quadrilateral cartilage, (a) blood-vessels. 
