﻿OrillACANTllA. 93 



OPIIIACANTHA Mull. & Troscii. 



Type op the Genus, 0. spinuhsa Mull. & Trosch. 



Disk -with little thorny spines. Katlial shields covered. Teeth ; 

 mouth-papillfe ; no tooth-papillaa. Spines numerous, slender, minutely 

 thorny ; arranged on the sides of the side arm-plates. Side arm-plates 

 meeting nearly, or quite, above and below. Two genital slits, begin- 

 ning outside the mouth-shields. 



SPECIES HEREIN DESCRIBED. 



0. spinuhsa. 

 0. setosa. 



Ophiacautlia spinulosa Mull. & Trosch. (Figs. 6, 7.) 



Ophiacantha spinulosa Mull. & Trosch. Syst. Asteriden, p. 107. 



Ophiocoma arctica Mull. & Trosch. Syst. Asteriden, p. 103. 



Ophiacantha gronlandica Mull. & Trosch. AViegm. Archiv. fur Naturg., p. 183. 1844. 



OpUocooia echinulala Forbes. Sutherland's Journal. Appendi.x. 



Ophiacantha spinulosa Lutken. Addit. ad Hist. Oph., p. 65. 



Sj^jecial Marks. — Disk evenly covered with short spines. 



Descrijjtion of a Specimen. — Diameter of disk, 9.5""°- ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 5°"°- ; 

 width of arm without spines, 1.7°"- ; length of arm, 42™ ; distance 

 from outer side of mouth-shield to mner points of teeth, to that 

 between outer corners of mouth-slits, 2.1 : 2.6. Mouth-papihEe, six or 

 seven to each angle of mouth ; standing well apart ; two outermost on 

 each side small, flattened, somewhat rounded, blunt ; innermost one 

 sharp, rounded, conical, resembling the lowest tooth, which also might 

 well enough be considered as a mouth-papilla. Teeth seven, thin, 

 rather long, flat, with a rounded cutting edge ; lowest one narrowest ; 

 uppermost one split in two. Mouth-shields much broader than long ; 

 outer side curved, lateral ends pointed ; a rounded peak within ; length 

 to breadth, .8 : 1.5. Side mouth-shields meeting within, long, slender, 

 of nearly equal width. Under arm-plates squarish, with an angle 

 within, and their outer corners rounded ; separated by side arm-plates ; 

 length to breadth (seventh plate), .8 : .7. First plate broader than long, 

 and about one half as large as those near it ; plates close to tip of arm, 



