long, broadly V-shaped in direct lateral view, with the proximal and distal edges parallel; the 

 proximal and «.listal edges are slightl) everted; the former bears a few short irregularly placed 

 spines <>n the margin; the latter bears on either side of the median line about eight regular 

 teeth which begin one third <>f the distance trom the median line and gradually increase in 



;h to the lateral corners; this row of teeth is continued inward toward the median line by 

 sin. ill spines of decreasing size; the lateral edges are slightly produced and smooth; the ant<i" 

 il angli i few prominent blunted spines; there is a prominent and sharp, though 



not especially high, median keel. TIn- IBr, (axillaries) are broadlv rhombic, with the lateral 

 angles truncated, about twice as broad as Ion-; the lateral edges, which are not quite so long 

 as those of tli' [Bi . are produced and irregularly and coarsely spinous; the distal edges and 

 the outer portion of the proximal edges are slightly everted and finely spinous; a prominent 

 keel, resembling that on the IBr,, runs nearly their whole length. 1 1 Br 4(3 + 4) (nine present), 



mbling the IBr series and, like them, prominently carinate; the lateral borders of the 

 elements of the IlBr series are produced and irregularly denticulate or spinous. III Hr 4(3+4) 

 (nine present), resembling the II Br series; the ossicles of the division series and of the arm 



s have produced and irregularly denticulate lateral borders as far as the base of P., externally, 

 and as far as the fifth or sixth brachial internally. 



The arms are 28 in number, about 120 mm. long, resembling those of O. gigatitea\ 

 the first two brachials are carinate; the following have slightly everted and finely spinous distal 

 edges, and the dorsal (hut not the dorsolateral) surface covered with very numerous short fine 

 spines; as the brachials become triangular the proximal edges gradually lose their eversion. 

 while that ol the distal edges becomes recumbent and more prominently spinous, and the 

 spinosity of the dorsal surface gradually becomes arranged in definite lines, becoming a series 

 ol sharp serrate longitudinal striations. 



The disk, especially along the ambulacral grooves, is thickly beset with small rounded 

 plates which become produced along the ambulacra; side and covering plates are well developed. 

 Pi, is from 14 mm. to 16 mm. long, composed of 28 — 30 segments, comparatively 

 slender as in the two other species of the genus, and tapering very gradually to a delicate 

 tij); all of the component segments are broader than long; the distal outer and distal inner 

 margins of the segments are sharply and very prominently carinate, this carination being very 

 spinous, and on the proximal portion of the inner margin coarsely denticulate; a shallow concave 

 through runs between these ridges; the proximal segments are more or less spinous on the 

 proximal (dorsal) surface. Pp is like IV. but not nearly so long nor so large. P, is 14 mm. 

 long with 26 segments, similar to l'i, hut more slender with the component segments somewhat 



er and their produced borders more spinous, and the distal edges of the outer produced 

 and spinous. P. is 8 mm. long with 17 segments, much more slender than P, with longer 

 segments distally which have more produced and spinous distal edges. The following pinnules 



ime progressively more slender with progressively longer segments which have coarsely 



spinous distal ends. P is 7.5 mm. long; I', is - mm. long; P. is 6.5 mm. long; 1' is 6 mm. 



The distal pinnules are 13 mm. long, composed ol' iS — 20 segments; the crest of the 



mat ie ridge is finely spinous. 



