30 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



Genus COLOBOMETRA A. H. Clark. 



COLOBOMETRA CHADWICKI, new species. 



Antedon serripinna Chadwick, Journ. Linn. Soc. (Zool.), vol. 31, 1908, p. 44 



(Suez Bay). 

 ? Oligometra serripinna A. H. Clark, Amcr. Naturalist, vol. 43, 1909, p. 255. 



Description. — Centrodorsal thin discoidal, the polar area broad and 

 flat, 2 mm. in diameter; cirrus sockets arranged in a single closely 

 crowded marginal row. 



Cirri XVI, 22-24, 12 mm. to 14 mm. long; first segment short, the 

 following gradually increasing in length to the third or fourth which, 

 with the remainder, is about as long as broad; second and following 

 segments with the distal dorsal edge produced into a finely spinous 

 transverse ridge which gradually becomes crescentic, in dorsal view, 

 then V-shaped, on the tenth segment parting in the middle and on 

 the last four or five before the antepenultimate becoming a pair of 

 small erect median spines; antepenultimate segment with a single 

 median spine; the dorsal processes are rather high, reaching about 

 one-quarter of the lateral diameter of the segments; opposing spine 

 large and prominent, triangular, terminal, arising from the whole 

 dorsal surface of the penultimate segment, and one-half as high as 

 that segment ; terminal claw slightly longer than the penultimate seg- 

 ment, stout, strongly curved basally, but becoming straighter dis- 

 tally; the distal ventral edge of the cirrus segments is slightly 

 produced and very finely spinous. 



Radials even with the edge of the centrodorsal ; IBr 2 oblong, slightly 

 over twice as broad as long, not in contact basally; IBr 2 long, pen- 

 tagonal, about as long as broad, the lateral edges nearly or quite as 

 long as those of the IBi\. 



Ten arms about 90 mm. long; first two brachials subequal, slightly 

 wedge-shaped, the first about twice as broad as the median length, 

 interiorly united for its proximal half or two-thirds, the distal halves 

 of the inner edge diverging at a right angle ; the second is somewhat 

 longer; third and fourth (syzygial pair) about as long as broad; fol- 

 lowing five or six approximately oblong, about twice as broad as long, 

 then becoming triangular, as long as broad, and distally wedge-shaped, 

 about as long as broad, longer than broad terminally ; IBr series and 

 brachials in the proximal fourth of the arm with a faint narrow 

 median keel; proximal triangular brachials with slightly produced 

 distal ends. 



P a absent; P x 7.5 mm. to 8 mm. long, very slender, evenly tapering 

 from the base to the tip with sixteen segments, the first broader than 

 long, the second about as long as broad, the following gradually 

 increasing in length, after the seventh being three times as long as 

 broad; the outer segments have slightly spinous distal ends; P 2 



