282 THE VOYAGE OF H.M.S. CHALLENGER. 



Fig. 4. Magnified view of the abactinal system. 



„ 5. Magnified portion of test seen facing the median ambulacral line. 



„ 6. Magnified portion of test seen facing the median interambulacral line. 



„ 7. Portion of test adjoining actinostome of same. 



„ 8. Smaller specimen (n. s.) seen from the actinal side (one with banded shoes, fig. 3, 



PI. v.). 



„ 9. Magnified portion of test facing median ambulacral line, from fig. 8. 



„ 9 a. Magnified portion of test of fig. 8, facing median interambulacral line. 



„ 10. Magnified portion of test of fig. 8, adjoining actinostome. 



„ 11. Still smaller specimen (n. s.), seen from the actinal side. 



,, 12. Magnified portion of test of fig. 11, seen facing the median ambulacral line. 



,, 13. Magnified portion of test of fig. 11, seen facing the median interambulacral line. 



,, 14. Magnified abactinal area of fig. 11. 



,, 15. Jaws of large specimen magnified. 



,, 16. Long, slender- pedicellarise among the primary radioles of test, magnified. 



,, 17. Short, spherical pedicellariae, mainly found in space adjoining the bare part of 



the abactinal region of the median interambulacral space, magnified. 

 ,, 18. The opposite view of fig. 17. 

 ,, 19 a, h, c, d. Difi"erent forms of straight, primary radioles, mainly from the actinal 



edge of the test, and below the equatorial line of test ; all natural size 



except d (f ). 

 ,, 20 a, h, c. Different forms of radioles, from the actinal side (f ), 

 ,, 20 d and 21 d are small radioles, closely packed near abactinal region of test in both 



areas (f ). 

 ,, 21 a, b, c. Different radioles from the actinal region of test ; all natural size except 



,, 22 a, h, c. Primary curved radioles, mainly from the equatorial region of test ; 



natural size. 

 a' c are figures of a and c seen from above, to show the triangular shape of the 



shaft of the radioles. 

 „ 22 d. Radiole, with flattened shoe, found near actinal edge of the test (f ), similar to 



that of the Arbaciadse. 



PLATE VP. 



Echinus horridus, A. Ag. (figs. 1-5), p. 115. 



Fig. 1. Abactinal system (f). 

 „ 2. Part of side of test to show the size of the spines ; natural size. 



