220 Mr. F. A. Bather on British Fossil Crinotds : 
less ; it is rounded and somewhat swollen above (Pl. XIII. 
figs. 1, 2,6, 9). The plates of which it is composed are 
hexagonal in the proximal region, but distally they become 
irregular in outline. The size of the plates varies consider- 
ably, but their transverse diameter is as a rule between 1°d 
and 2°5 millim., their vertical diameter being rather less. 
The plates are sometimes quite smoothly rounded or aimost 
flat (Pl. XIII. fig. 1) ; sometimes they are slightly folded at 
the edges, the folds being at right angles to the sutures 
(Pl. X11]. fig. 9): in E 6002 this folding is very clearly 
marked, and at the same time it is quite obvions that there 
are no pores or slits within the folds (Pl. XIII. fig. 8). In 
the separate distal end of a sac shown in PI. XIII. tig. 6, the 
surface of the plates appears rather curiously pitted; this, 
however, is no doubt due to weathering, and may be com- 
pared with the roughness already alluded to (Pl. XIII. fig. 7). 
The Tegmen is unknown. 
The Stem (Pl. XIII. figs. 1 and 13; zincotype, p. 211, 
fies. 2 and 3) is round, composed of ossicles which alternate 
both in height and width with fair regularity. The following 
are a few measurements of the heights of the ossicles :—In 
E 6004 (fig. 2, p. 211) the respective heights of the ossicles 
are about 1:16 millim. and °59 millim.; in 57362 B. M. they 
are 1 millim. and *55 millim.; in 57864 B. M., in a more 
proximal part of the stem, the ossicles are of three sizes with 
heights 1 millim., °75 millim., and +2 millim, ‘The width of 
the stem is between 5 millim. and 7 millim. The lumen is 
quinquelobate and its diameter is about 4 that of the stem, or 
a little less. The articular surface of each ossicle is slightly 
concave, and is radiately striated. In the longitudinal sec- 
tion the space between the concave articular surfaces is filled 
with transparent calcite, while the lumen itself is filled with 
opaque matrix. ‘This probably results from the fact that the 
interarticular ligaments decayed more gradually than the 
axial cord and its blood-vessels, and that, after the place of 
the latter had been taken by infilling ooze, they themselves 
were gradually replaced by the infiltration of carbonate of 
lime. We may now note, both in the longitudinal and trans- 
verse (fig. 8) sections, that the stereom of the ossicles is 
separated from the matrix in the canal by a thin film of 
calcite; this too, then, must represent some lining membrane 
or ligament. 
The base of the cup is often slightly excavated for the top 
columnal (PI. XIII. fig. 4). 
