156 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



laterally. The IBrz (axillaries) are pentagonal. The IIBr and IIIBr series are 2, but 

 the latter are developed only on the outer side of the IIBr axillaries so that there are 

 normally 6 arms to each postradial series arranged in 2, 1, 1, 2 order. But one IIIBr 

 series is undeveloped. The 29 arms are 60 mm. long and consist of about 100 smooth 

 and rounded segments of which the first few are discoidal and those following triangu- 

 lar, about as long as broad, but becommg quadrate farther out. The first syzygy is 

 between bracliials 3+4, the second is about brachials 19+20 or 20 + 21, and the distal 

 intersyzygial interval is 4-10 (usually 6 or 7) muscular articulations. Pa is absent. Pi 

 is always absent on the mnermost of every two arms arising from a IIIBr axillary, and 

 sometimes also on the arms which are borne directly on the IIBr axillaries. But it is 

 sometimes present on these latter arms, and always on the two outermost arms of each 

 postradial series, though varying in size, consisting of 12 or 15 segments most of which 

 are longer than broad. P2 and Pb are sometimes twice as long as Pj, reaching 12 mm. 

 in length and consisting of about 18 elongated segments with spines at their distal 

 ends. P3 is not half the size of P2 and Pb, and is smaller than Pi, wliile the pinnules 

 of the next pair (P4 and P^) are the smallest on the arm, after which the length of the 

 pinnules increases slowly. The disk is 8 mm. in diameter, very much incised, and 

 quite naked. Saccuh are very abundant on the arms and pinnules. As preserved in 

 alcohol the skeleton is reddish brown, the perisome rather darker. 



I examined this specimen at the British Museum in 1910. The longest cirrus 

 segments are scarcely longer than broad. The dorsal spmes on the outer cirrus seg- 

 ments are not nearly so broad as those in the specimens described as Antedon disci- 

 Jormis, resembling rather those of the form described as Cyllometra albopurpurea. 

 Dr. Gisl^n, who examined it in 1925, said that the arm bases are well separated, and 

 that the intervals between the syzygies are long. 



Carpenter said that this is a very singular species the general relations of which 

 are with Antedon marginata {= Stephanometra protectus) and A. aequipinna {Lam- 

 promeira palmata) ; but it is distinguished from them both, and from all other species 

 with the IIBr series 2, by the peculiar distribution of the pimiules. The arrangement 

 of the arm divisions seems to be like that of Pentacrinus {=Diplocrinus) maclearanus, 

 IIIBr axillaries being developed only on the two outermost of the four secondary arms 

 on each postradial series, so that the groupmg of the arms is 2, 1, 1, 2. One one 

 postradial series, however, a IIIBr axillary is missing, so that the total number of arms 

 is 29 and not 30 as it otherwise would be. 



Pa is always absent, as is also the case in Antedon {Cyllometra) disciformis and in 

 Decametra injormis, and Pi is also absent in some arms. It is undeveloped on the 

 inner arm of every pair which arises from a IIIBr axillary, and it is occasionally also 

 absent on the two imier arms of the postradial series which are borne directly on the 

 IIBr axQlaries; though it is sometunes present on these, and it is always to be found 

 on the two outermost arms of a postradial series. Of the two single arms which are 

 borne on the inner faces of the two IIBr axillaries, one may have P2 while it may be 

 absent from the other, and there appears to be no constancy as to its occurrence in 

 this position. When present it is somewhat smaller than the corresponding pinnule 

 on the outside of the postradial series. The large P2 and Pb are tolerably equal on all 

 the arms, P2 being perhaps a little the longer. But P3 is much smaller again, and the 

 pinnules of the next pair (P4 and Pa) still more so, barely reaching 4 mm. The disk 



