S8 



BULLETLX 82, UNITED STATE>S NATIONAL MUSEUM 



first brachials. The fii-st syzygial pairs, composed of the third and fourth brachials, 

 are longer inwardly than outwardly, about twice as broad as the median length, \\-ith 

 the pro.xinial and distal edges concave. 



The ne.xt si.x or seven brachials are wedge-shaped with concave ends, about twice 

 as broad as the median length, the following ones then becoming almost or quite tri- 

 angular, about as long as broad, and later gradually wedge-shaped again and ter- 

 minally elongate and more or less constricted centrally. The ends of the brachials 

 arc smooth and not produced. 



Sj'zygies occur between brachials 3 + 4, Q-flO, 14 + 15, and distally at intervals 

 of 3 niusciUar articulations. 



Pi is from 8.5 to 10 mm. long, with 14 to 20 segments, and resembles Pj. Pj is 

 from 9 to 10.5 mm. long, ^^^th 15 to 18 segments, of which the first is broader 

 than long, the second is slightly longer than broad, and the remainder are greatly 

 elongated. Pa is from 8.5 to 11 mm. long with 14 to 20 segments which are propor- 

 tionately slightly shorter than those of P2; this pinnule resembles P2 but tapers very 

 slightly less rapidly and therefore appears very slightl.y stouter. Pa is similar to Pi. 

 The distal pinnules are from 7 to 9 mm. long with 16 or 17 segments which bej^ond 

 the second are greatly elongated with finely spinous distal edges. 



The color in alcohol is white or whitish \nth a broad median band of yellowish, 

 reddish or purplish brown on the division scries and arms which commonly breaks 

 up into narrow transverse bands distally; there are sometimes large blotches of pur- 

 plish brown on the pinnules, and the perisome may be browTi or dark purple. Some 

 specimens are almost uniform whitish. 



Table 2. — Details of some specimens of Iridometra adrestine from published records 



Notes [by A.M.C.].— In studying Dr. Mortensen's Japanese collection, Gislen 

 (1927) had five specimens, of which three were immature and had P3 relatively smaller 

 than in the larger specimens, where it tended to be the same size as Pi and Pj. He con- 

 cluded from this that /. melpomene is nothing more than the young of adrestine. Mr. 

 A. H. Clark seems to have decided independently of Gislen that these two are s^Tion- 

 ymous, since this part of the typescript was wiitten about 1923. 



In 1928 Gislen named a specimen in the British Museum from the Challenger 

 collections Iridometra adrestine, though it was taken at station 219 in the Admiralty 

 Islands, north of New Guinea, well beyond the known range of this species. The 



