36 



Basal plates depressed, anchylosed and form a pentagonal disc 

 about two and a half times as wide as the diameter of the column. 

 Subradials a little the largest plates in the calyx, hexagonal, with- 

 out reference to any division of the basal disc, length and width 

 nearly the same, almost wholly within the basal concavity, not 

 visible in a side view. First radials slightly smaller than the sub- 

 radials, heptagonal, a little wider than long, rest on the outer rim 

 of the truncated base of the calyx, and each one bears a short 

 central spine, which, by reason of the position of the plate, is 

 directed downward at an angle of about forty-five degrees. Second 

 primary radial smaller than the first, longer than wide, hexagonal, 

 inferior lateral sides the longest, most convex in the central part. 

 Third primary radials very little smaller than the second and a 

 little less convex, length and width subequal, part of them hep- 

 tagonal, others hexagonal, and support on each superior sloping 

 side two secondary radials, and in one ray shown in our specimen 

 there are three secondary radials. The secondary radials are sub- 

 equal in size and somewhat smaller than the third primary radials. 

 The last secondary radials bear the cicatrix for the support of the 

 arms, at the top of which there is an ambulacral orifice. There 

 are, therefore, ten arms and ten ambulacral openings to the vault 

 in this species. 



There are three intersecondary plates in each area, one fol- 

 lowed by two, which unite with the plates of the vault, without 

 any distinct line of separation. These two plates, at their inferior 

 ends, separate the superior ends of the second secondary radials, 

 and their superior ends separate the ambulacral orifices, and 

 interlock with the plates of the vault. 



There are only two regular interradial areas completely pre- 

 served in our specimen and each of these contains thirteen plates. 

 The first plate is a little smaller than a first primary radial, hexag- 

 onal, rather, wider than long, broadly truncates a subradial, bears 

 a short central spine, and is followed by three plates in the sec- 

 ond range. There are also three plates in the third range and 

 above these there are three ranges of two plates each, the last 

 two of which are surmounted with two plates belonging to the 

 under side of the so-called pseudo-brachial appendages. 



The vault is nearly flat, gently convex over the ambulacral 

 areas and slightly depressed, in the interradial areas, until the 

 depression is cut short by the so-called pseudo-ambulacral append- 



