PLATE IV. 



OPHIUROIDEA. 



Figure 1. OPHIOPLEURA ARCTICA, Duncan. The upper part of the disk and arms, natural size. 



2. The under surface of the disk, magnified. 



2 a. The teeth on the jaw-plate, oblique view, magnified. 

 2 b. The teeth, from above, magnified. 

 2 c. The teeth, approaching, magnified. 



3. OPHIOGLYPHA SARSII (Liitken). From above, natural size. 



4. The underpart of the disk, magnified. 



5. OPHIOGLYPHA ROBUSTA (Ayres). From above, natural size. 



6. The underpart of the disk and an arm, magnified. 



7. The upper surface of the disk, magnified. 



8. OPHIOCTEN SERICEUM (Forbes). The upper surface, slightly magnified. 



9. The scaling of the upper part of the disk and part of an arm, magnified. 



10. Part of the underpart of the disk, magnified. 



11. OPHIACANTHA SPINULOSA. The upper surface, natural size. 



12. Part of the under surface, magnified. 



13. The spines on the disk, magnified. 



14. OPHIOCTEN SERICEUM (Forbes). Part of the disk-scaling, magnified. 



15. AMPHIURA HOLB(ELLI. Part of the underpart of the disk, magnified. 



16. Radial shields, magnified. 



17. Side view of the arm, magnified. 



