Boo7ie, Echinodermata, Cruises of "Ara" and "Alva" 147 



Material examined: One specimen, brought up on anchor 

 chain, Seba-Seba Bay, South Brother's Island, Dutch East Indies, 

 October 21, 1931. 



Technical description : Disk pentagonal, diameter 8 milli- 

 meters, arms each 67 millimeters long. Abactinal surface of disk 

 paved with large to medium-size suboval, subcircular and other 

 irregular polygon-shaped plates. These plates are smaller in the 

 series extending inward from the arms, while the wide inter- 

 brachial areas are pouchlike, covered by much wider plates toward 

 the circumference, frequently only two wide plates covering the 

 entire outer upper border of an interbrachial area. The actinal 

 surface is paved with plates similar to those of the abactinal, which 

 on the actinal surface tend to decrease in size toward the center. 

 The genital slits are smooth and large, extending from the angle of 

 the mouth plate almost to the circumference of the disk. The mouth 

 shield is small, nearly as wide as long, 0.9 millimeter wide, 1 milli- 

 meter long, heart-shaped with the apex directed inward. The side 

 mouth shields are narrowed inwardly into large triangles placed 

 wedge-like, one on either side of the central shield with the apices 

 not meeting; the outer angle of each side mouth shield is widened 

 into a rounded process that touches the first under arm plate. The 

 mouth frame is subrectangular with the two halves meeting 

 within. There are ten mouth papillae to each jaw angle, five on 

 each side. These are short, thick, with the distal margin wide, 

 blunt, slightly rounded. The apical tooth is large, blunt, squarish. 



The under arm plate is axe-blade shape, about 0.8 millimeter 

 long, and 0.6 millimeter greatest width, yet appearing almost 

 squarish, with the distal margin definitely rounded, the lateral 

 margins equally concave and the proximal margin actually nearly 

 straight or slightly convex but appearing slightly concave because 

 of the overlapping adjacent blade. There is only one tentacle 

 scale which is oval, very large and broad, about 0.4 millimeter 

 long and 0.2 millimeter wide. Each side arm plate supports three 

 strong spines, of which the median is about one-fourth longer 

 than the ventral which is about subequal to the dorsal spine. These 

 spines are strong, tapered, blunt-tipped, laterally compressed, 

 having two opposed sides definitely much wider than the remain- 

 ing region. The arm spines are transversely banded with alter- 

 nating dark brown and cream in the present alcohol-preserved 

 specimen. The side arm plates extend well up on the dorsal sur- 



