256 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The cirri are XV-XVII, 29-36 (usually 35 or 36), 30 mm. long. They are 

 moderately stout basally but taper very gradually to a slender tip. The first segment 

 is short and those following gradually increase in length to the fourth or fifth, which 

 is about as long as broad, the remainder being slightly longer than broad. The 

 terminal 10 to 14 segments may have a slight dorsal carination. The opposing spine 

 is small but prominent, terminal or subterminal, and is equal to one-third the width 

 of the penultimate segment hi height. The terminal claw is somewhat longer than 

 the penultimate segment and is slender and slightly curved. The segments in the 

 distal half or two-thirds of the cirri have purple saddle-shaped markings. The 

 radials may be entirely concealed in the midradial line, or they may be equal to half 

 the length of the IBr^ The IBr] are oblong, short, five or six times as broad as long, 

 and laterally in contact. The IBr 2 (axillaries) are short, almost or quite triangular, 

 two and one-half to three tunes as broad as long. The IIBr series are 4(3+4) in 

 one of the specimens two of them are 2 and are in close lateral apposition and 

 flattened against their neighbors. One of the two specimens possesses a single IIIBr 

 2 series, which is developed internally. 



The 15-20 arms are 140 mm. long, and are elongated, slender, and evenly 

 tapering. The first two brachials are subequal in size, slightly wedge-shaped, three 

 to four times as broad as long in the middorsal line. The first syzygial pair (composed 

 of brachials 3 + 4) is oblong, two and one-half or three times as broad as long. The 

 next five brachials are approximately oblong, nearly four times as broad as long in 

 the median line. The following brachials are triangular, somewhat over twice as 

 broad as long with the longer side somewhat convex, after the proximal fourth of the 

 arm becoming wedge-shaped, about three tunes as broad as long, and slightly longer 

 terminally. Syzygies occur between brachials 3+4, again from between brachials 

 14+15 to between brachials 29 + 30, and distally at intervals of 11 to 19 muscular 

 articulations. 



P D is small and weak, about 6 mm. long, and composed of 13-16 segments, all 

 of which are about as long as broad. PI is similar but slightly larger, 7 or 8 mm. 

 long. P 2 is 9 to 12 mm. long with 18 segments, much stouter and stiffer than the 

 preceding pinnules, and ending abruptly with a stiffened tip more or less as in the 

 species of Stephanometra. The first two segments are not so long as broad, the third 

 is about as long as broad, and the remainder are longer than broad, becoming twice 

 as long as broad distally. The pinnule may be slightly carinate basally, and after 

 the second or third the distal dorsal ends of the segments become thickened and project 

 strongly, forming lateral processes resembling those in the type of crenulata. P 3 is 

 slightly stouter and slightly longer than P 2 , but similar to it though usually with a 

 few less segments. P 4 is 9 mm, long, comparatively slender, and its segments do not 

 bear lateral processes; the segments become about as long as broad on the fourth or 

 fifth and about twice as long as broad terminally. The following pinnules are similar, 

 gradually increasing to 10 mm. in length, and then becoming more slender and slowly 

 decreasing to 8 mm. in length. The color in alcohol is white, the segments in the 

 distal half or two-thirds of the cirri with purple saddle-shaped markings. 



The type specimen of Antedon crenulata was thus described by Carpenter: 

 The centrodorsal is a thick convex disk 5 mm. in diameter with a single or partially 

 double row of cirri. The cirri are about XX, 30+. The sixth segment is longer 



