REPORT ON THE ORINOIDEA. 33 
Iil.—THE CALYX. 
In all the recent Crinoids, with the single exception of Thawmatocrinus (P]. LVI. 
figs. 1-4), the calyx proper is formed of but two series of plates, viz., the basals, which rest 
upon the top stem-joints, and the radials, which are supported by and alternate with the 
basals. The plates of these two series are suturally united to their fellows and to one 
another; and they enclose a central cavity which is sometimes large enough to contain 
the whole visceral mass, as in Holopus (Pls. I-IV.) and Hyocrinus (Pl. VI). In 
other cases, however, the internal cavity of the calyx is reduced to a minimum, and it 
lodges nothing but the chambered organ with the plexiform gland which rises from it ; 
while the entire visceral mass is situated altogether above it, and is very easily detached 
from it, as in many Comatule, so that there can hardly be said to be any cup at all. 
Intermediate conditions between these two extremes are met with im the Bourgueti- 
crinidee and Pentacrinide. In the last named family the cup which is formed by the 
united upper surfaces of the radials is wider than in Antedon, but somewhat more 
hollowed than in Actinometra (Pl. XII. figs. 1, 2, 15, 16; Pl. XVII. fies745, 5)25 Pla XOK: 
figs. 5,8; Pl. XXVI. fig. 11; Pl. XXX. figs. 3, 4; Pl. XXXII. figs 556 Pl UX, 
figs. 7,8; Pl. L. figs. 5, 6); and the lowest portion of the visceral mass rests in this 
concave upper surface of the radial pentagon ; while the greater part of it lies in the cup 
which is formed by the outer radials and lowest distichals (P]. XVI. fig. 5; Pl. L. fig. 1; 
Pl. LXII.). But the central funnel of the calyx, which is between the inner faces of 
the radials, only contains the plexiform gland ascending from the chambered organ 
(Pl. LVIII. fig. 3, ~). 
This is also the case in Rhizocrinus and Bathycrinus (Pl. VIIb. figs. 1, 4, 5, x). In 
the former genus the upper surface of the calyx has a deep hollow which lodges a portion 
of the intestinal coil (Pl. X. figs. 1, 4, 6, 7, 8); while the upper part of the visceral 
mass is entirely supported by the first four brachials in two syzygial pairs (Pl. X. 
figs. 2, 20). In Bathycrinus, however, the gut hardly descends to the level of the first 
radials ; and though the visceral mass is very largely supported by the large wing-like 
processes of the axillaries, it is practically quite free from the lowest brachials (Pl. VII. 
fig. 3;, Pl. VIIb. figs. 1, 7, 8). 
Concealed in the lower portion of the calyx is the chambered organ, the position of 
which, relatively to the calyx-plates, varies considerably. In all the Comatule it is lodged 
within the cavity of the centro-dorsal, and it is therefore entirely on the dorsal side both 
of the radials and of the basals, whether the latter have been metamorphosed into a 
rosette or not. But in the stalked Crinoids there is no enlargement of the central 
canal of the stem within its uppermost joint, and the vascular axis passes up into the 
calyx before expanding to form the chambered organ. In Rhizocrinus, Bathyerinus, and 
(z00L, CHALL. EXP.—PART xxxu1.-—1884.) id 
