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



Table of Species of Ojihiactis — continued. 



Disk scales thick and swollen : upper arm plates wide, transverse oval, not \ 



swollen. Side mouth shields making a connected ring. Four or five V Ophiactis simplex. 

 stout hut not swollen arm spines. Small disk spines, . . . I 



Differs from Ophiactis simplex in wanting disk spines; in radial shields scarcely ) 



to he distinguished from scales (wliich are less imbricated than in simplex) C Ophiactis arenosa. 

 and in more oval upper arm plates, . . . . . ' 



Disk scaling coarse, and with few or no spines. Three or four stout, blunt, \ 



tapering arm spines. Two or three mouth papillas on each side. Teeth > Opjhiactis cuspidata. 

 lobed, . . . . . . . . . ) 



Disk without spines, and covered with thick, rounded scales, whereof the \ _ . . 

 largest are near the radial shields. Two small tentacle scales, . . J ' 



Disk scales coarse, and set with numerous short spines. Eadial shields short \ 



and triangular. Four stout, cylindrical, tapering arm spines. One mouth V Ophiactis noma. 

 papilla on each side. Five arms, . . . . . . ) 



Mouth shields very wide and short. Always one mouth papilla on each side, • 

 four to five stout smooth long arm spines, usually blunt and tapering, but 

 sometimes the upper ones much swollen; middle ones longest. Disk scales J- Ophiactis kroyeri. 

 coarse above and below with variable number of spines. Eadial shields 

 larger than in the type Ophiactis balli, .... 



J 



Ophiactis hirta. 



Large (disk 11-12 mm.) nearly black. Four arm spines; upper one longest. \ 



Radial shields shagreened, small, and rudely diverging. Under arm plates f ,-,,.,. 



° ' J ° ° r > Ophiactis nigrescem. 



curved without and within ; re-enteringly curved on sides. Upper arm I 



plates truncated fan shape, . . . . . . ' 



Five short, smooth, tapering arm spines. Disk scales smooth and rather fine. \ 



Upper arm plates rounded fan shape, not swollen. One mouth papilla on > Ophiactis maculosa. 

 each side, . . . . . . . . ' 



Disk finely scaled, and set with short, minute spines. Radial shields small 

 and pear-seed shaped. Four moderately stout tapering arm spines, the 

 uppermost longest. Two or three minute mouth papilla? on each side. 

 Seven arms, 



Disk scales coarse and thick, with large radial shields ; no spines except a few \ 



near the margin. Four rather long and slender arm spines, the upper one > Ophiactis poa. 

 longest. Two mouth papillae on each side, . . . . ) 



Disk scales larger in centre, where primary plates may be distinguished in ai 



rosette; no spines, or only an occasional minute one on the margin. I „ Jiactis canotia 

 Three or four rather long and tapering arm spines Two mouth papilla; \ 

 on each side, . . . . . . . . > 



Four long, rather slender arm spines. Many strong disk spines. Disk scales \ 



thick and somewhat irregular. Two mouth papilla; on each side. \ Ophiactis abyssicola. 

 Teeth lobed, . . . . . . . ) 



Structure more delicate. One mouth papilla. Radial shields very small. \ 



Disk scales small, fine and regular. Four arm spines about as large as in r Ophiactis canica. 

 Ophiactis asperula. Upper arm plates clean, transverse oval, . . ' 



