A MONOGKAPH OF THE EXISTING CBINOIDS 323 



in size up to their final length of about 5 mm. P,, P 2 , and P 3 are somewhat longer 

 than the corresponding pinnules (P a , P b , and P c ) on the inner side of the arm. The 

 proximal segments of all these pinnules are short and broad, and in the eight or nine 

 first pairs are prominently and sharply keeled. 



The disk is 8 mm. in diameter and is deeply incised. The sacculi are large and 

 crowded on the pinnules, forming two very irregular rows. They are not found on 

 the disk. 



The centrodorsal and cirri are white, the arms are flesh colored with chocolate- 

 brown bands between the brachials, and the disk is light gray-brown. 



The preceding description is adapted from Hartlaub's description of the type 

 specimen in the Gottingen Museum. 



Notes. — The two specimens collected during the course of the Ceylon Pearl Oyster 

 Fisheries investigations, one at station lvii and the other at station xxiv, both have 

 11 arms, a single IIBr 4(3+4) series being present in each. The color when living 

 was black. 



The type specimens of H. aspcra from Singapore may be thus described: The 

 centrodorsal is moderately thick, discoidal, with the bare polar area slightly convex, 3 

 mm. in diameter, and having a more or less pitted surface. The cirri are XVII, 

 26-31, from 17 mm. to 22 mm. in length, and moderately slender. The first segment 

 is short and those following gradually increase in length to the fifth or seventh, which 

 is about as long as broad. The succeeding segments are similar, or slightly longer than 

 broad, after about the twelfth or thirteenth, which is a more or less marked transition 

 segment, decreasing in length, soon becoming as long as broad and so continuing to 

 the end. The segments beyond the transition segment have moderate sized blunt 

 dorsal spines. The opposing spine is much larger than the spines on the preceding 

 segments. The radials are almost entirely concealed by the centrodorsal. The IBrj 

 are short and bandlike. The IBr 2 (axillaries) are almost triangular, two to two and 

 one-half times as broad as long. The IIBr series are 4(3+4). The division series 

 as far as the base of P D are in close apposition and laterally flattened against each other. 

 The synarthrial tubercles are rather prominent. The arms are 14-18 in number, 60 

 mm. long. The brachials are very short with, except for the first few discoidal bra- 

 chials, strongly produced distal ends. 



P D is 7 mm. long, moderately stout basally but tapering rapidly in its proximal 

 half and becoming slender and flagellate distally. It is composed of 24 segments, 

 which are at first twice as broad as long or even broader but become as long as broad 

 distally. The larger proximal segments are strongly carinate. Pj is similar to P D , of 

 the same length or slightly longer, and of the same size basally but tapering somewhat 

 less rapidly. P 2 and P 3 are the same length, 9 mm. long, about as stout as P! basally 

 but tapering much more gradually and hence appearing larger, and somewhat stiffened. 

 They consist of 24 segments which at first are broad, becoming about as long as broad 

 at about the middle of the pinnule, and elongate distally; the proximal segments are 

 strongly carinate. P 4 is of the same character as the pinnules preceding but is smaller, 

 only 6 mm. in length. P 6 is slender, small, and weak, 3 mm. long. The following 

 pinnules very slowly increase in length, reaching 5 mm. distally. The color in alcohol 

 is dark brown. 



