98 B1 1.1. I.I EN 92* 1 Ml I.D STATES NATIONAL MUSKI M 



occur between brachials 3+4, again al about the thirty-first brachial, and distally 

 itt intervals of 13-15 muscular articulations. P D and P P are large and stout, P P 

 being rather the longer. They are composed of 40-50 segments of which the lower 

 arc large bul oot specially marked and those following diminish in size but gradually 

 dcvclo [> a projection of the dorsal edge at their distal end which disappears in the 

 smaller terminal segments. The third and following pinnules decrease rapidly both 

 in length and in stoutness, after which the length slowly increases again. The disk 

 ambulacra are protected by a well-developed calcareous plating, which ceases at the 

 arm bases. The anal tube is also considerably plated, but the other interambulacral 

 areas are unprotected. Sacculi are very abundant on the pinnules. The color in 

 alcohol is brownish white, with the perisome mottled with gray. 



The specimens from Challenger station 187 were described by Carpenter as a 

 new species under the name Antedon multiradiata. According to Carpenter the centro- 

 dorsal is a thick and slightly convex disk. The cirri are marginal. The cirri are XX- 

 XXV, 40-50 + , rather long. Few or none of the segments are longer than broad, and 

 those in the distal half have a small blunt spine projecting slightly forward. The 

 opposing spine is strong and sharp. The radials are visible. The IBri are short 

 and free laterally, and are united to the IBr 2 by syzygy. The postradial series are 

 quite free and may divide four times, the division series being 4(3+4). There are 

 about 40 arms, composed of short and smooth triangular brachials, which become 

 blunter and squarer toward the arm ends. Syzygies occur between brachials 3+4, 

 the next anywhere from between brachials 17 + 18 to between brachials 46+47, and 

 those succeeding at intervals of 8-20 muscular articulations. P D is of moderate 

 length and is composed of about 25 stout segments. The pinnules following gradually 

 decrease in size to P If and P 2 and P b are considerably smaller. The succeeding 

 pinnules increase slowly in size but never become very large. The disk is much 

 incised and is paved with large plates between the ambulacra, which are elevated 

 ridges with plated walls; but the plating scarcely extends beyond the level of the 

 outermost axillary. The disk is about 15 mm. in diameter, and the arms are prob- 

 ably about 60 mm. long. I examined these two specimens in the British Museum 

 and found them to be small examples of the present species. 



Bell described Antedon microdiscus, which was based upon a single specimen from 

 Port Molle in 22 meters, in the following terms: The centrodorsal is rather large and 

 prominent, bearing marginal cirri in 2 or 3 rows. The cirri are XXX-L, 50-70, 

 nearly 50 mm. long. None of the cirrus segments are markedly longer than broad. 

 As a rule the distal two-thirds bear an inconspicuous dorsal spine, and the opposing 

 spine is hardly more conspicuous. The radials are visible. The radials and the 

 elements of the IBr series are very short and wide, and the IBr, are not in lateral 

 contact. The IIBr series are 4(3+4). "Three palmars, the axillary normally a 

 syzygy- The arms may divide again, and of the three joints the axillary may or 

 may not be a syzygy." There are probably as many as 90 arms in an adult. The 

 arms are stiff and straight and about 150 mm. in length. The earlier brachials have 

 fairly even edges and are well rounded dorsally and flattened laterally. Those suc- 

 ceeding are faintly wedge-shaped, the distal edge of each projecting alternately on 

 each side mto a slight protuberance. The arms generally, though slender, are very 

 linn and still and are set very close to one another. Syzygies occur between brachials 



