220 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



of the articulation between the elements of the IBr series. The division series are in 

 close lateral contact. The 35 arms are nearly 125 mm. long and consist of 200+ bra- 

 chials. The first syzygial pair (composed of brachials 3+4) and the next four or five 

 brachials are oblong, and the following brachials are short, sharply wedge-shaped, and 

 very slightly overlapping, twice as broad as long. About the middle of the arm the 

 brachials become more equal sided, and they are nearly oblong in the terminal por- 

 tion. Syzygies occur between brachials 3+4, again from between brachials 12 + 13 

 to between brachials 16 + 17, and distally at intervals of from 7 to 13 (usually 9 or 

 10) muscular articulations. 



P D is quite short. P P , PI, and P 2 are rather longer. They all have somewhat 

 the appearance of being in two parts, as if they had been broken and had regenerated. 

 The lower half consists of wide and thick segments with dorsal keels, while the outer 

 half is composed of quite small segments and grows, as it were, out of the middle of 

 the wide lower portion. This is least marked on P2, which is nearly twice as long as 

 PI and is stouter and more uniformly tapering. P 3 is still longer, reaching 25 mm. 

 in length and consisting of about 50 broad segments, of which the lower are keeled. 

 P 4 is nearly as long but is less stout. On the inner side of the arm the seventh bracliial 

 bears a large pinnule (P c ) like the preceding one (P 3 ). That on the fifth brachial 

 (P b ) is much smaller, and that on the ninth (P d ) is variable, sometimes small and 

 sometimes nearly as large as its fellow of the fourth pair. In some arms the fourth 

 or eighth segments may bear the largest pinnule (that is, P 2 or P 4 may be the largest). 

 Beyond the fourth pair (P 4 and P a ) the length decreases, rapidly at first but after- 

 ward more gradually until about the twentieth (twenty-second counting syzygial 

 pairs as two brachials) brachial beyond which the pinnules are tolerably uniform 

 in size, decreasing again toward the arm tips. The carination of the basal segments 

 of the lower pinnules dies away gradually and is lost after the tenth pair. The disk 

 is naked and much incised, 15 mm. in diameter. Sacculi are closely set along the pin- 

 nule ambulacra. The color is deep purple, almost black. 



Hartlaub wrote that the type specimen of Antedon bipartipmna, which he ex- 

 amined at Hamburg, at first gives quite the same impression as one of the specimens 

 from Amboina which he identified as Antedon ludovid ( = Heterometra amboinae; 

 see page 297). The most striking features are afforded by the cirri, which are long 

 and stand in a single row and have no opposing spine or terminal claw. But Hart- 

 laub said that one cannot attribute great weight to these features, since certain aspects 

 of the specimen point to an abnormal development. First of all, there is the irregular 

 position of the first brachial syzygy. On many arms it lies between brachials 3+4, 

 on others between brachials 2+3, and on still others there is a syzygy between brach- 

 ials 3+4 and another between brachials 5+6; in individual cases the first brachial 

 syzygy is between brachials 12+13 or 13 + 14. Concerning the peculiarities of the 

 lower pinnules Hartlaub said that it is a fact that they have been broken off and 

 regenerated. Their structure, however, corresponds completely to that characteristic 

 of the lower pinnules of A. ludovid. He said further that both species further agree 

 in the possession of both IIIBr 2 and IIIBr 4(3+4) series. Carpenter's statement 

 that the IIIBr series are usually 4(3+4) but sometimes 2 is not correct. The speci- 

 men has many more IIIBr 2 than IIIBr 4(3+4) series, and indeed the inner IIIBr 

 series are for the most part 2. 



