gg BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



out like a cup, instead of being cut square off or slightly rounded. General covering 

 of plate consists, on actinal surface, of ovate or oblong lanceolate spmelets, which 

 become capillary in fasciolar furrows; outer end of plate bristles with slender, sharper 

 lancet-like spinelets those on sides of the broad f asciolar grooves, frequently with fine 

 mucronate tips. Spinelets adjacent to the spines are enlarged. The f asciolar 

 grooves between plates are very deep, the specialized ridges being about as thick, 

 when denuded, as the adjacent grooves. These ridges, when viewed from actinal 

 surface, extend laterally beyoml the bottom of groove a distance equal to the width 

 of the plate, measured from bottom of groove to inner (actinal) edge. 



Terminal plate small, granulous, as wide or wider than long, not notched toward 

 paxillar area. 



Adambulacral plates fairly massive with a curved furrow margin. Armature 

 consists of (I) a furrow series of six strongly compressed, round-tipped spines, the 

 two centrally situated the longest (3.75 to 4 nmi.) and the others graduated in length. 

 Commonly the edge of spine toward furrow is broader than that from it. Frequently 

 there are but five large spines (rarely but four), the sLxth being much smaller than 

 the rest and placed back slightly from the edge at either end of series. Rarely 

 seven furrow spines are present. (2) On actinal surface are two or three irregular 

 longituilinal scries of much smaller and slenderer spinelets which decrease rapidly 

 in size as they recede froni furrow. Series adjacent to furrow spines consists of about 

 three or four tapering pointed spinelets, one-half to two-thirds the length of median 

 furrow spines. The outer one or two series are very irregular; sometimes there is 

 no regular serial arrangement at all. The average plate is best shown by the figures. 



Mouth plates large and prominent actinally, the combined pair broadest at 

 about the middle. Armature consists of (1) a furrow or marginal series of seven to 

 nine, sunilar in character to median spines of adambulacral furrow series, which begin 

 at about middle of plate and form a fairly straight series to inner angle, increasing in 

 size as they })roceed inward, the inner two or three being broad, flat, and knife-like 

 and in common with the others the edge away from furrow is often thinner than that 

 toward it. (2) A(;tinal surface is covered with slender spaced spinelets which 

 increase in size toward the suture and iimer angle. 



Actinal intermediate areas large, the plates being arranged in regular series 

 parallel with furrow, and also in regular series leading from marginal to adambulac- 

 ral plates. The breadth of ray near extremity is largely due to the intermediate 

 plates, of which four longitudinal series extend 0.39 length of ray (measured from 

 interradial angle); three series, 0.65 or slightly more; two series, 0.7 to 0.8; and the 

 series adjacent to adambulacrals extends about half way between end of latter and 

 tip of ray or about 0.85 total length. In the interbrachial angle there are additional 

 short series; for instance, in a large specimen, a fifth series extends nearly 0.25 length 

 of ray, a sixth to the third or fourth inferomarginal; and counting along interradial 

 line, there are nine or ten plates between the first inferomarginal and third adambu- 

 lacral (see pi. 13, fig. 2). The plates are strongly carinated, the keel rumiing trans- 

 versely, each being surmounted by a prominent paxilliform tuft of spinelets, of which 

 the peripheral are very slender and pointed, while the central are usually much 

 stouter, often clavate and three to five sided in section, with flattened flaring tips 

 cut obliquely, which appear to be bent outward toward marginal plates. In such 

 specimens the spinelets of series adjacent to adambulacrals are heavier, often sub- 



