CLARK: OPIIH'KOIDEA. 449 



pentajijonal or almost trianfjiilar, about .40 mm. loni; and not quite 

 so broad; third similar l>ut .smaller; beyond the thirfl .segment there 

 are no under arm-plates. Side arm-plates relatively very large, 

 meeting completely both above and below. Along the median line, 

 on both the upper and lower surfaces of the arm, is a conspicuous 

 longitudinal groove or furrow. Each side arm-plate bears 3 or 4 

 very minute, sharp spinelets of rather unequal size; the largest are 

 not equal to one third the length of the segment. Tentacle-pores 

 present only in connection with the second and third under arm- 

 plates; they are very minute, lie near the proximal angle (or side) 

 of the plate, and have no tentacle-scales. Entire under surface of 

 animal shagreened. Color (dried): — very pale brown. 



Station 4732. Eastern Tropical Pacific, 16° 32' 30" S., 119° 59' W., 

 2012 fms. Bott. temp. 34.8°. Glob. oz. 



One specimen. 



The remarkable reduction in the number of plates composing the 

 disk and arms of this Ophiomusium is really notable. Without 

 upper and under arm-plates (save on the lower side of two basal 

 joints), with no tentacle-scales, and with a disk composed of only 

 about 65 plates, the species is not likely to be confused with any of 

 those, hitherto known. 



Ophiomusium glabrum. 



Lutken and Mortensen, 1899. Mem. M. C. Z., 23, p. 132, pi. 4, fig. 7-9. 



The present large series seems to show that this is the characteristic 

 brittle-star of the deep waters of the Eastern Tropical Pacific. The 

 specimens range from 5 to 33 mm. across the disk. 



Station 4647. Eastern Tropical Pacific, 4° 33' S., 87° 42' 30" W., 

 2005 fms. Bott. temp. 35.4°. Lt. gy. and br. glob. oz. 



Station 4649. Eastern Tropical Pacific, 5° 17' S., 85° 20' W., 2235 

 fms. Bott. temp. 35.4°. Ene. stky. gy. m. 



Station 4651. West of Aguja Point, Peru, 111 miles. 2222 fms. 

 Bott. temp. 35.4°. Fne. stky. gy. m. 



Station 4656. West of Peru, 6° 55' S., 83° 34' W., 2222 fms. 

 Bott. temp. 35.2°. Fne. gn. m., mang. nod. 



Station 4658. West of Peru, 8° 30' S., 85° 36' W., 2370 fms. 

 Bott. temp. 35.3°. Fne. gn. m., mang. nod. 



Station 4666. West of Peru, 11° 55' S., 84° 20' W., 2600 fms. 

 Bott. temp. 34.9°. Fne. gy. rad. oz. 



