NOTOCRINIDAE 195 



Description. The largest specimen has arms 105 mm. long. The single specimen 

 from St. 1948 has shorter but much more massive arms; it is considerably older than 

 any of the others and is as robust as big specimens of A^. virilis. The species has much 

 shorter cirri, shorter stouter pinnules and smaller gonads, than A^". virilis. 



The centrodorsal may be conical or hemispherical with a bare and smooth dorsal 

 pole (Fig. 20 a). The ventral edge is produced into small corners or low wide projections 

 interradially. In some of the younger specimens the corners are raised into ridges free 

 of cirrus sockets; in the others and in the older specimen they are occupied, like the 

 rest of the centrodorsal, with closely placed cirrus sockets. 



Cirri XXXVIII-LX or more, 21-32 (Fig. 20 b). The cirri are composed of stout 

 segments and they are strongly curved ; having but half as many segments as those of 

 A^. virilis they are much shorter in proportion to the size of the animal. Their segments 

 are not uniform in length as in A^. virilis. The first three are short, the fourth or fifth is 

 as long as broad. The fifth or sixth to the ninth or twelfth are longer than broad — less 

 so in old specimens than in Fig. 20b, which is from a young specimen. Those beyond 

 gradually become shorter until the distal are wider than long. On one of the segments 

 between the sixth and the fifteenth a small projection appears at the distal end of the 

 dorsal side; it gradually develops into a strong low keel occupying nearly the whole 

 of the dorsal side of the more distal segments. The terminal claw is small and the 

 opposing spine is not well developed: when most strongly developed it is more keel- 

 than spine-like. In the old specimen both claw and spine are much smaller than in the 

 figure. The cirrus segments may be all of one colour, white or dirty white ; or the first 

 six or more may be of a darker colour, usually yellow, than the distal. The last three or 

 four, including the terminal claw, may also be dark in colour. 



No basal plates are visible. 



The shapes of the radials, costals, axillaries and lower brachials of the younger 

 specimens are shown in Fig. 20 a. The radials are large and in lateral contact ; the con- 

 tact is not always complete as in the figure, the distal corners may be free. The proximal 

 margin of the radial is convex ; the distal edge is wider and concave. The costals are 

 not in contact with one another. Each forms a shoulder with the posterior projection 

 of the axillary which incises it. The costals are narrower distally than proximally. The 

 proximal edges of the axillary are nearly straight, the distal are concave. 



The radials and the costals are of very different shapes in the old specimen from St. 

 1948. The radials are reduced to narrow strips, perhaps one-tenth as long as wide. The 

 costals are in lateral contact for about half their length ; the lateral edges of the distal 

 half bend sharply inwards towards the axillary so that the distal width of the ossicle is 

 about three-quarters of the greatest proximal width. 



Syzygies are numerous. The first is normally between the third and fourth brachials 

 but in one arm of one specimen it is between the eleventh and twelfth. The second is 

 usually between the ninth and tenth though it occurs also between the sixth and seventh, 

 the eighth and ninth, and between every pair from the tenth to the sixteenth. The third 

 is usually between the fourteenth and fifteenth and those beyond are numerous to the 

 end of the arm with one to four or more brachials between each pair. 



