16 



OPHIURA. 



DESCMPTIOX OF GEXERA AND SPECIES. 



OPHIURA Lamk. {non Forbes). 

 Type of the Genus, 0. Icevis. 



Ophiitra Lamk. Syst. des Anim. sans Verteb. 1801. 

 0/-/aWerma MiJLL. and Tkosch. Syst. Asterid. 1812. 



Disk granulated ; teeth and mouth-papillae ; no tooth-papilloe ; spines 

 essentially smooth, shorter than the joints, flattened, numerous (7 to 13), 

 arrano-ed along the outer edge of the side arm-plates ; two tentacle- 

 scales, the outside one covering the base of the lowest arm-spine ; no 

 ray-scales ; an indentation in the back of the disk, where it is joined by 

 the arm; four genital slits, the first pair beginning outside the mouth- 

 shields. 



GROUPING OF SPECIES HEREIN DESCRIBED. 



Arm-spines equal, 



vSide mouth-shields covered, 0. breincauda. 



I 0. brevis/nna. 



Lowest arm-spines longest, - 



Side mouth-shields naked, 



With radial shields, 



Without radial shield? 



0. Hohnesii. 

 0. oUvacea. 

 0. Junuarii. 

 0. Icevis. 

 0. cinerea. 

 0. rubtcnnda. 

 0. panamensis, 

 0. teres* 

 0. appressa. 



Ophiura brevicauda Lyman. 



Ophioderma brevicauda Lijtken ; A^'idensk. IMeddelelser. Jan., 1856. 

 Ophioderma brevicauda Lxjtken ; Addit. ad Hist. Oph. 94. 



Special Marks. — Granulation very coarse; arm-spines unusually short 

 and stout; arms generally not more than three or three and a half times 

 the diameter of disk. 



Description of a Specimen. — Diameter of disk, 20"™ ; from outer side 

 of mouth-shield to outer corner of opposite mouth-slit, 7°""" ; width of 

 arm, without spine.s, o.S""""- ; length of arm, 77'"™-; the distance from 

 outer side of mouth-shield to inner points of teeth is to that between 

 outer corners of mouth-slits as 3 : 4.2 ; mouth-papillae, eighteen ; outer 



* The largest specimens have the radial shields often covered. 



