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



Fig. 10. Ophiohelus umbeUa , IjJTO.. , \5. A joint close to tip of arm, digested with 



potash ; seen from above. On the upper 

 side is the film-like upper arm j^late pierced 

 with niimerous holes ; to the right and left 

 of it is a side arm plate, also of open structure, 

 and having a spine ridge which consists of 

 two or three crowded, irregular rows of 

 elono'ated mamelons. On the right these 

 mamelons are shown carrying their parasol 

 spines. Underneath are the curious, curved, 

 translucent bars that are the two halves of 

 the arm bone, united only at their articu- 

 lating ends. 



„ 1 1. ,, „ ^j^. Scales of disk, one of them bearing a minute s^^ine 



cleaned with potash to show their open struc- 

 ture, and the mode of growth of the spines. 



,, 12. Ophiochytra epigrus, L}Tn., below, f. (The mouth angle is not correct. 



There should be a sm;dl ja-w plate at the apex, 

 the outer mouth papilla should be lai'ger, and 

 the first under arm plate slightly forked.) 



„ 13. „ „ above f. 



,, 14. „ „ arm joints in profile f. 



„ 15. Ophiacantha placentigera, Lym., below, f. 



„ IG. „ „ above, f. 



,,17. ,, „ ann joints in profile, f-. 



PLATE XXIX. 



Fig. 1. AmpMura angularis, Lym., below, f . 



„ 2. „ „ above, f. 



,,3. ,, „ arm spines, f . 



,, 4. ,, dilatata, Lym., below, ^j*. 



„ 5. ,, ,, above, \^. 



,, 6. ,, ,, a side arm plate with its spines in profile, \+. 



,, 7. ,, lanceolata, Lym., below, with one arm complete, \'*. 



,, 8. ;, ,, above, with one arm complete, ^j*. 



,, 9. ,, „ a side arm plate with its spines in profile, \*. 



,, 10. ,, tomentosa, Lym., below, f . 



„ 11. „ „ above, f. 



,, 12. ,, ,, a side arm plate with its spines in profile, ^. 



