PART 5 A MONOGRAPH OF THE EXISTING CRLNOIDS 85 



Diagnostic features. The centrodorsal is conical, as high as broad at the base; 

 P 2 and P 3 have about 15 segments; the distal edges of the brachials are not strongly 

 everted. 



Description. The centrodorsal is conical, 3 mm. broad at the base and 3 mm. high; 

 the cirrus sockets are arranged in six closely crowded alternating rows. As a whole the 

 centrodorsal resembles closely that of the species of Hathrometra. 



The cirri are about LXX; but none are present in the only known specimen. 



The radials extend slightly beyond the edge of the centrodorsal, and are separated 

 by a narrow V in the interradial angles. The IBrj are about three times as broad as 

 long, not in contact basally, with the lateral edges converging distally. The IBr 2 

 (axillaries) are rhombic with the free lateral edges rather longer than those of the IBri 

 with which they form somewhat more than a right angle. There is a moderately de- 

 veloped synarthrial tubercle on the articulation between these ossicles. 



The 10 arms are about 60 mm. long. The first brachials are longer exteriorly 

 than interiorly, slightly incised by the second brachials, with their inner edges entirely 

 free and diverging at approximately a right angle. The second brachials are nearly 

 twice as large as the first, irregularly quadrate in form, with a rounded posterior process 

 incising the first. The third and fourth brachials (the first syzygial pair) are together 

 about as long as broad. The following eight or nine brachials are slightly wedge-shaped, 

 half again as broad as long, the following becoming almost or quite triangular, about as 

 long as broad, and further out on the arm wedge-shaped again and longer than broad. 



Syzygies occur between brachials 3+4, 9+10, and 14 + 15, and distally at intervals 

 of 3 muscular articulations. 



Pi is about 6 mm. long, very slender and delicate, somewhat stiffened, composed 

 of about 9 segments of which the first is about as long as, or slightly longer than, broad, 

 the second and third are twice as long as broad, and the following gradually increase in 

 length, becoming exceedingly elongated distally. P 2 is about 10 mm. long, proportion- 

 ately stouter than PI and stiffer, with 15 segments, of which the first is about as long as 

 broad, the second is slightly longer than broad, the third is twice as long as broad, and 

 the remainder are from three to four times as long as broad. P 3 is 8 mm. long with 15 

 segments, similar to P 2 but shorter and slightly less stout. P 4 resembles P 3 . P 5 is 

 5 mm. long, slightly more slender than P 4 , with 10 segments which have slightly everted 

 and spinous distal ends. The following pinnules are similar. The distal pinnules 

 are lacking. 



The color in alcohol is light brownish yellow with traces of a broad median dorsal 

 line of purple. 



Locality. Investigator station 15; north of Port Blair, Andaman Islands; 205 

 meters; dark mud; November 29, 1888 [A. II. Clark, 1909, 1912] (1, I.M.). 



Remarks [by A.M.C.]. The high conical centrodorsal of this species marks it off 

 from A. psyche and from all the other species of the Antedoninae, since the removal of 

 Hybometra to the Zenometrmae. Specimens complete with cirri may indicate its re- 

 moval from the genus, or even the subfamily. However, the small number of segments 

 in PI distinguishes it from the Bathyrnetrinae, the larger P 2 from the Perometrinae, 

 and the alternating cirrus sockets from the Zenometrimte, which are the only other 

 subfamilies of the Antedonidae to which it might possibly be referred. 



