32 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



APOROMETHA OCCIDENTALS H. L. Clark 



[See vol. 1, pt. 1, fig. 92 (p. 151); pt. 2, fig. 205 (p. 141)] 



Ptilomclra macronema (part) A. H. CLARK in Michaelsen and Hartmeyer, Die Fauna Siidwest-Aus- 

 traliens, vol. 3, Lief. 13, Crinoidea, 1911, p. 461 (small specimens from Koombana Bay, 14J^-18 

 meters) . 



Aporometra occidenlalis H. L. CLABK, Mem. Mus. Comp. Zool., vol. 55, 1938, p. 42 (in key), p. 43 

 (description; Koombana Bay, Bunbury, 5-8 fathoms), p. 45 (Garden Island); Echinoderm fauna 

 of Australia, 1946, p. 58 (in key), p. 59 (common at Koombana Bay and Garden Island, Fre- 

 mantle, Western Australia). 



Diagnostic features. The longest cirrus segments are from half again to twice as 

 broad as long. The arms are 25-30 (usually about 25) mm. long, and the cirri are XX, 

 39-61 (usually 40-50), from 20-27 (usually about 25) mm, long. 



Description. The centrodorsal varies from low hemispherical to a broadly rounded 

 truncated cone, and from nearly twice as broad as high to about as high as broad. 

 The cirrus sockets are arranged in 10 columns of 3 or 4 each. The columns may be 

 closely crowded with the sockets all more or less angular, or the two uppermost sockets 

 in each radial area may be separated in the midradial line by a bare slightly depressed 

 area. The cirrus sockets are deep with sharply sloping sides and a large slightly reni- 

 form central fulcral ridge about twice as broad as high with an oval central perfora- 

 tion, the central fulcral ridge being separated from the sloping sides by a depressed 

 bandlike area. 



The cirri are XX, 39-61 (usually 40-50), from 20-27 (usually about 25) mm. 

 long. The first two segments are somewhat over twice as broad as long, the second 

 slightly longer than the first, and the third and following are about twice as broad as 

 long, in the terminal third of the cirri becoming slightly shorter. The cirri taper 

 slowly from the base to the distal fourth, thence slightly more rapidly to the tip. The 

 segments in the terminal fourth are broadly flattened dorsally so that when viewed 

 from the end they are much broader than high, ventrally strongly and evenly convex, 

 dorsally only very slightly convex and here roughened with 8 to 12 fine parallel glassy 

 narrow, more or less irregular and sometimes branched or anastomosing, longitudinal 

 ridges similar to those on the ventral and lateral surfaces. The dorsal surface of the 

 antepenultimate segment is slightly more convex than that of the segments preceding. 



The radials project slightly beyond the rim of the centrodorsal. Their distal 

 border is slightly concave. The IBrj are about three times as broad as the median 

 length with the lateral borders produced and the lateral edges straight or very slightly 

 concave and parallel or slightly diverging; the distal edge is slightly concave in the 

 median third and slightly bowed outward in the lateral thirds. The IBr 2 (axillaries) 

 are broadly rhombic, with broadly truncated lateral angles, and are about twice as 

 broad as long. The lateral edges are short, from a third to a half again as long as 

 those of the IBr t with which they form a straight line. The proximal border in the 

 median third has a broadly rounded convexity incising the distal border of the IBr t . 

 The distal sides are slightly concave and make with each other an angle of somewhat 

 more than 90. 



The 10 arms are 25 to 30 (usually about 25) mm. long. The first brachials are 

 about twice as long exteriorly as interiorly, and about twice as broad as the exterior 

 length. The second brachials are of about the same size but the distal border is some- 

 what more oblique. The first syzygial pair (composed of brachials 3+4) is slightly 

 longer interiorly than exteriorly and is about as broad as the interior length. The 



