94 



OPHIACANTHA SPINULOSA. 



small, shield-shaped, with a regular angle inward, their length less than 

 that of the line of juncture of the two side arm-plates. Side arm-plates 



larg;e, meeting above and below the whole 

 length of the arm. Upper arm-plates Inroad 

 triangular, with outer side gently curved, a 

 rounded angle within, and the lateral corners 

 pointed; length to breadth (fifth plate), .7:1.4 ; 

 close to tip of arm, the plates are heart-shaped, 

 and very minute, and bear a very small pro- 

 portion to the side arm-plates, which cover 

 almost the whole surface. Disk evenly and 

 closely covered, above and below, with short, 

 stout cylinders, ending in a rounded crown of 

 fine thorns ; those on the under surface shorter and less thorny ; about 

 20 to a square mm. Arm-spines long, slender, slowly tapering, covered 



with longitudinal rows of microscopic thorns ; 

 near the disk eight, fiirther out seven ; lengths 

 to that of under arm-plate (fourth joint), 2, 2, 

 2, 1.8, 1.5, 1, .8, .8 : .8. One tentacle-scale, 

 longer than broad, rounded at the end ; length 

 to that of under arm-plate, .5 : .8. Color, in 

 alcohol : above, light umber ; below, paler, 

 except the interbrachial spaces, which are 



Ophiacantha spinulosa. (Lower side.) v.icixiv»^j.. 



Ophiacantha spinulosa. (Upper side.) 



Fig. 7. 



Variations. — O. spinulosa attains the size of 14™°"- ; the disk spines 

 are then less thorny, and are longer than in the young. 



This species has been found at Eastport, Maine ; and at Grand Manan 

 Island (twenty fathoms, shelly bottom, Stimpson) ; Newfoundland (Stu- 

 witz) ; West Greenland (Rudolph, Olick, HoUboll) ; Spitzbergen ; and 

 on the northwest coast of Norway, from North Cape to the Lofoten 

 Islands, living on corals, nulUpores, and ascidia, m from twenty to thirty 

 fathoms (Sars). 



