324 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



of the axillaries, sometimes also the proximal border, like the distal border of the IIBr 2 

 (in IIBr 4[3+4] series) and the lateral borders of the IIBr, are everted and dentate. 

 The ornaments of the IIIBr series have already developed the entirely spiny or dentate 

 character. The ornamentation of the lower brachials of this specimen shows the Spinosa 

 type in its highest development. The brachials bristle with pointed spines and sharp 

 teeth that are sometimes single, sometimes more or less coalesced. Especially favored 

 are the distal edges of the brachials; particularly from the fourth to about the tenth 

 bracliial the surface of the brachials is beset with smaller teeth and spines. On syzygial 

 pairs there are only two transverse rows of spines, one directly beneath the other. 

 The distal limit of this ornamentation varies on different arms from the tenth to the 

 seventeenth brachial. On the surface of the brachials immediately following are found 

 only isolated and sometimes obsolescent granules; their distal ends are at first beset 

 with rather high spines which later become smaller and more sparse, and finally dis- 

 appear toward the arm tips. 



The sequence of the syzygies is rather variable. In arms arising from a IIBr 

 axillary the first syzygy may be between brachials 1+2, followed by another between 

 brachials 4 + 5; or these two syzygies may be absent, in which case the first syzygy is 

 found between brachials 11 + 12 or 14 + 15. A syzygy from between brachials 19+20 

 to between brachials 23+24 appears to follow regularly, and the next follows at inter- 

 vals of from 6 to 9 muscular articulations. On arms arising from a IIIBr axillary the 

 first syzygy as a rule is between brachials 1+2, often followed by another between 

 brachials 3 +4. The syzygy between brachials 1 +2 is rarely absent, but if it is the first 

 syzygy is between brachials 3+4. The next syzygy, which is sometimes the second 

 and sometimes the third, is from between brachials 13 + 14 to between brachials 23+24, 

 and the distal intersyzygial interval is from 4 to 14, usually 7-10, muscular articulations. 



P D is 15-17 mm. long and is composed of 30-40 short segments of which the first 

 8-12 are much broadened and are keeled into a hatchet-shaped edge on one side. PI 

 is 10-12 mm. long with about 30 segments of which the lowest 6-8, with the exception 

 of the two first, show the typical carination. The length of the lower pinnules appears 

 to vary, as on one arm Hartlaub found PI about 11 mm. long and P 2 15 mm. long with 

 about 28 segments. In general the length of the following pinnules as far as P 4 and 

 the number of their component segments decreases. P< is 8-10 mm. long with 15-20 

 segments. In the range of the ornamentation of the arms the keels of the first 2-4 

 pinnule segments are often beset with spines or teeth. The pinnules of the middle of 

 the arms, after the tenth brachial, are 6-7 mm. long with 10-12 segments of which the 

 two first are short and those following elongate. Where gonads are present the third 

 and fourth segments are markedly broadened. Toward the arm tips the pinnules be- 

 come more slender and their length and the number of component segments increases. 

 The distal pinnules are about 10 mm. long with up to 15 segments. 



The ambulacral plating consists of prominent side and covering plates. The sac- 

 culi are of medium size and rather conspicuous. The disk is about 20 mm. in diameter 

 and is only slightly incised. 



The arm length is estimated at 140 mm. 



In alcohol the disk is gray-brown, the skeleton light gray. The centrodorsal is 

 somewhat darker than the other parts. Only the cirri are white. 



Locality. Blake station 249. 



