Boone, Echinodermata, Cruises of "Ara" and "Alva" 133 



69 meters ; Tawi Tawi Islands, Sulu Archipelago, 12 meters ; Pearl 

 Bank, Sulu Archipelago, 15 meters; Pulu Tongkil, Sulu Archi- 

 pelago, 13 meters ; Great Sangir Island, 45 meters ; Gebe Isle, 31 

 meters; anchorage, south of Timor, 34 meters; Rotti Isle, 34 

 meters; Station 310, 8^ 30' S., 119° 7.5' E., 73 meters ("Siboga" 

 Stations, Koehler) ; Sulu Archipelago : near Siasi and also near 

 Tawi Tawi Islands, three specimens ("Albatross") ; Anamba Bay, 

 Malay Straits, "Ara" Station (Boone). 



Material examined : Four specimens in excellent condition, 

 taken in 30 fathoms, at Anambas Isle, Lat. 3° N., Long. 106° East, 

 eight miles west of Terampa Cove, Siantan Island (in the Malay 

 Straits, northeast of Singapore), by the "Ara." 



This species appears to have its center of distribution in the 

 Dutch East Indies-Philippines area, the "Ara" specimens from 

 the Anambas Islands adding another locality for it in the Malay 

 Straits. 



Technical description : The disk is pentagonal to subcircu- 

 lar in outline, diameter, 7.5 millimeters ; arm length, about 70 mil- 

 limeters. The entire abactinal surface, except the paired radial 

 plates, is covered with numerous upright conical spines from 0.8 

 to 0.5 millimeters high, which occur from 0.5 to 1.0 millimeter 

 apart, of irregular sizes and irregularly spaced, these spines 

 averaging a greater height near the circumference of the disk 

 and becoming increasingly more numerous, smaller and sharper 

 near the center. Similar spines occur on the circumferal margin 

 and on the interbrachial region of the actinal surface where they 

 are very numerous and acuminate. These disk spines are of two 

 types : (a) the conical acuminate spines with the spinulose lateral 

 margins and two or three spines clustered at the apex; and (b) 

 club-spines, which are thicker, cylindrical with thickened spinu- 

 lose apices and with spinules also on the lateral margins. The 

 radial plates are covered but show an elongate, narrowed pear- 

 seed shape, extending inward two-thirds of the radius of the disk, 

 with the outer margins the wider, truncated, with a rounded inner 

 angle ; the inner lateral margins are relatively straight, well sepa- 

 rated, except at the inner lateral angles, diverging obliquely from 

 these angles to the apices, which are separated from each other by 

 a distance equal to the width of the outer margin of one plate ; the 

 region between these plates bearing a double series of coarse 

 upright spines, like those on the remainder of the abactinal sur- 



