317 



" Surface of the calyx marked by small, short, branching grooves, which 

 radiate from the centre and anastomose at the margins of large plates of 

 irregular shape. The exact outlines of some of these plates are not clearly 

 defined in any of the three specimens that the writer has seen, but two of 

 the latter have part of the calyx crushed in such a way as to shew parts 

 of the margins of at least two of the radials and of one of the basals. Jud- 

 ging by these indications of the outlines of the plates and by the peculiar 

 sculpture of others, the composition of the calyx would seem to be essenti- 

 ally as follows. In the undivided and lower moiety of the divided portion 

 there appears to be a circlet of large subpentagonal and presumably basal 

 plates, immediately above the column. On the surface of theseplates the 

 branching grooves radiate upward and outward, but not backward, and, 

 consequently, only the front and part of the lateral margins of each of 

 these plates is minutely sinuated. Next to these supposed basal plates 

 and alternating with them there is a circlet of five large radials. These 

 radials are irregular in outline, but their margins are minutely sinuated 

 all round, except in the middle of the summit, where each of these plates 

 is overlapped by the distal portion of the ambulacral area, as shewn in 

 fig. 22. On each side of the anal region the upper and inner portions of 

 the margin of each of the two radials that partially bound it, are slightly 

 modified, as also shewn by fig. 22, in which A represents the relative 

 position of the middle of the anal region. In the upper and lobate por- 

 tion of the calyx there appears to be a comparatively small and presu- 

 mably interradial plate, whose outline it is not yet possible to define 

 precisely, in or near the middle of each of four of the lobes, the corres 

 ponding part of the fifth lobe being occupied by the group of small plates 

 which surround and apparently cover the anus. 



" The summit or entire surface above the calyx, is exclusively occupied 

 with five large linear lanceolate, radiating ambulacral areas, which extend 

 a little beyond and below the midheight and alternate, at and near the 

 centre, with five small narrowly elongated, subtriangular, almost bottle- 

 shaped plates. The ambulacral areas consist of well defined grooves, 

 which are partially and perhaps in perfect specimens were wholly roofed 

 over with two rows of small, transversely elongated and alternately ar- 

 ranged covering plates, from the centre of the summit, where they intei'- 

 lock and probably cover the presumably subtegminal mouth. In the only 

 specimens known to the writer these plates roof over the ambulacral 

 grooves, from the middle of the summit, for distances varying from one- 

 half to fully two-thirds of the entire length of each groove, but always, at 

 least, as far outward as to the bases of the small alternating subtriangular 

 plates. On some of the ambulacral grooves only eight covering plates can 

 be counted on each side, in a longitudinal direction, but on others there 



