26; 



the sockets of the two columns in each radial area are quite distinct 



from each other; the interradial ridges on the proximal portion of the 



centrodorsal are low, rounded and short 



d 1 basals separated from the centrodorsal at the interradial angles (Fiji) wyvillii 



d" basals everywhere in contact with the centrodorsal (Moluccas and 



Phi 1 ippi nes) sulcatits 



c 2 the 10 columns of cirrus sockets are closely crowded on a small sharply 

 conical centrodorsal ; the interradial ridges on the proximal portion of 

 the centrodorsal are high and sharp 

 d 1 centrodorsal with the sides more nearly parallel at the base than 



further out, and much longer than broad at the base (Carib- 



bean Sea) óalanoides 1 ) 



ór centrodorsal sharply conical, very slightly longer than broad at the 



base (western coast of Ir eland) helgae 



i. Atelecrinus siilcatus A. H. Clark. 



A. H. Clark. Notes from the Leyden Museum, vol. 34, 1912, p. 152. 

 Stat. 85. o°36'.5S., iio°29'.5E. Makassar Straits. 724 Metres. i Ex. 



The centrodorsal is sharply conical, 3 mm. broad at the base and 4 mm. in vertical 

 height. The cirrus sockets are arranged in ten columns four, more rarely five, to a column ; 

 the two columns of each radial area are close together; the columns of adjacent radial areas 

 are separated by shallovv furrows which basally are in width nearly equal to the diameter of 

 the adjacent cirrus sockets, but become gradually narrower distally ; the interradial separation 

 of the columns of cirrus sockets is always somewhat greater than the 

 midraclial separation. Each cirrus socket is bordered proximally and 

 laterally by a horseshoe-shaped rim which proximally scarcely rises above 

 the general surface of the centrodorsal, but on either side stands out as 

 high ridge so that in lateral view the sides of the centrodorsal appear 

 strongly serrate, the longer side of the teeth being gently convex, roughly 

 parallel with the dorsoventral axis, the shorter slightly concave, at right 

 angles to this axis. The ridges on either side of the cirrus sockets 

 gradually increase in thickness distally, but terminate rather abruptly just 

 after attaining their maximum height and thickness, so that the border 

 of the cirrus sockets distal to them is not raised above the general 

 surface of the centrodorsal. The basal outline of the centrodorsal as 

 viewed dorsally is pentagonal, each side of the pentagon being slightly 

 and evenly concave; five well marked rounded interradial ridges are (Courtesy of the u. s. Na- 



. ii- 1 j- 1 tional Museum). 



present which slowly decrease in height and disappear at about the distal 



border of the first cirrus sockets. These ridges mark the angles of the pentagon when the 



Fig. 16. 

 Lateral view of a specimen 

 of Atelecrinus siilcalus from 



1) Synonyms cubensis P. H. Carpenter and pourtalhi A. H. Clark. 



