CLARK: OPHIUROIDEA. ' 431 



tentacle-scales; second arm-pair, and following 10-15 pairs have a 

 single, cylindrical tentacle-scale; distally this scale is more and more 

 thickened and rough or even prickly at tip. Beyond basal part of 

 arm, each tentacle-pore is guarded by two scales, of which the outer 

 is much the smaller, scarcely half the size of the inner, which may be 

 o\er a millimeter long, considerably exceeding the arm-segment. 

 Color of dry specimen, dull cream-color. 



Station 3GSo. Off the Marquesas Islands, Eastern Tropical 

 Pacific, 830 fms. Bott. temp. 38°. Vol. s., glob. 



One specimen. 



This species is very different from A. sublaeve of the Galapagos 

 Islands and Panamic region, its nearest ally geographically. Nor 

 does it resemble any more closely the related forms of the western 

 Pacific. On the contrary it is really nearer to A. arenosum of the 

 West Ihdies than to any other species, so far as general appearance 

 and granulation of disk and arms is concerned. The size and arrange- 

 ment of the genital slits and the absence of a second tentacle-scale on 

 the basal arm-segments serve as excellent marks of distinction. 



Ophiacanthidae. » 

 Ofhiacantha contigua. 

 Liitken and Mortensen, 1899. Mem. M. C. Z., 23, p. 173, pi. 17, fig. 7-9. 



Six specimens, ranging in size from 4 to 6.5 mm. across the disk 

 agree very closely with the original description and figures of 0. 

 contigua. There are, Iiowever, more oral papillae, 4 or even 5 being 

 present on each side of each jaM^ 



Station 4621. Panama: off Mariato Point. 581 fms. Bott. 

 temp. 40.5°. Gn.s., gn. m., r. \ 



Ophiacantha cosmica. 



Lyman, 1878. Bull. M. C. Z., 5, p. 146. 1882. Challenger Oph., pi. 13, fig. 

 13-15. 



In addition to some excellent specimens, with disks ranging from 

 10 to 15 ram. across, there are some specimens from an unknown 

 station which are in wretched condition. 



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