j^g BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



P3. This, the only known specimen, is small with the length IBr, to Bro (inclusive) 



4.25 mm. 



Description..— The centrodorsal is flattened hemispherical, about three times as 

 broad 11s high, 1 .9 mm. broad at the base, with the w4de flat polar area measm-ing 1.3 mm. 

 in diameter. The ciiTiis sockets are arranged in three closely-crowded alternating 

 marginal rows. 



The cirri are about XXX, 10-12, from 3.7 to 5.0 mm. long. The first two segments 

 are about twice as broad aslong, the third is from a third to half again as long as the me- 

 dian width, and the fourth isabouttmce as long as the median width. The segments follow- 

 ing become graduaUy shorter, so that the antepenultimate is from a third to half again 

 as long as broad, and the penultimate is about as long as broad. The opposing spine 

 is moderate in size, terminal and directed outward. The terminal claw is slightly longer 

 than the penultimate segment, rather stout and rather strongly curved, most strongly 

 curved in the shorter cirri. The longer proximal cirrus segments are slightly constricted 

 centrally. The distal halves of the cirri are laterally flattened and dorsoventrally ex- 

 panded, so that in side view the outer half of the cirrus is about t^vice as broad as the 

 proximal half. The cirrus segments are all broadly rounded dorsaUy. 



The radials are even with the edge of the centrodorsal. The IBr, are very short, 

 seven or eight times as broad as long, with the pro.ximal and distal edges parallel and 

 the lateral edges strongly convergent and somewhat convex. The IBrj (axillaries) are 

 triangular, from a third to half again as broad as long, with the proximal border form- 

 ing almost a straight line, the two distal sides concave and the distal angle narrow and 

 rounded at the apex. The lateral angles of the IBr2 are separated from those of their 

 neighbors by a distance almost equal to the entire mdth of the ossicle. 



The 10 arras are all broken off near the base. The first brachials are wedge-shaped, 

 about three times as long exteriorly as interiorly. The second brachials are irregularlj- 

 quadrate, more than twice as broad as the median length; they are somewhat larger 

 than the first brachials. The first syzygial pair (composed of brachials 3+4) is broader 

 than long, and is longer interiorh* than exteriorly. The next two brachials are oblong, 

 half again as broad as long, and those following are obhquely wedge-shaped, nearly 

 as long as broad. The brachials bej-ond the fourth have prominent and very fineh" 

 serrate distal ends. 



Syzygies occur between brachials 3 + 4 and 9 + 10. The width at 3+4 is 0.7 mm. 

 and the length from IBri to the second syzygj is 4.25 mm. 



P, is 3 mm. long with about 20 short segments, which are flared at their distal ends 

 dorsally; the outer ones become about twice as long as broad. P2 is about 1.7 mm. long, 

 with 12 segments. P, is 2 mm. long, wnth about 13 relatively longer segments, of which 

 the first, second, and third have a triangular dorsal process armed with spines dhccted 

 obliquely distaUy, and the second to the sixth bear a fusiform gonad. Tlie follo\nng 

 pinnules resemble P3. 



The color is pale dull purplish, with a median white band on the division series 

 and arms. The centrodorsal and cirri are white, the latter with broad light purple 

 saddles on the segments and a dark purple interrupted midventral line. 



Locality. Mabahiss station 53; south coast of Arabia (lat. 19°22'36" N., long. 

 57°53' E.); 13.5 meters; rock, shingle, shells and lithothamnion ; November 2, 1933; 

 water temperature 22.79° C. [A. H. Clark, 1937] (1, B.M., 1937.2.25.24). 



