REPORT ON THE CRINOIDEA. 47 
IV.—THE RAYS. 
A. Tue Ray-privisions anp ARMS. 
The arms of a Neocrinoid, viewed in a strictly morphological aspect, must be regarded 
as commencing with the first joints beyond the primary radials. The same is the case in 
many Paleeocrinoids, of which Schultze says, “ Die Arme (brachia) beginnen unveriin- 
derlich da, wo eine deutliche Gelenkfacette eines festen Kelchstiickes ihren Ursprung 
”* In the Platyerinidze and other Palzeocrinoids, and in all Neocrinoids (except- 
anzeigt. 
ing perhaps Guettardicrinus), this articular face is on the first radial. In the five-armed 
Eudiocrinus indivisus the next joints beyond the radials are syzygial, with pinnules on 
the epizygals,’ which clearly shows that they must be considered as arm-joints and not as 
belonging to the calyx, although they undoubtedly represent the so-called second and 
third radials of a ten-armed Crinoid. The other species of Hudiocrinus have these two 
primitively separate joints not united by syzygy but articulated, just as in Thawmatocrinus 
(Pl. LVI. figs. 1-4). The second one bears a pinnule both in Thawmatocrinus and in 
Eudiocrinus varians; but in Hudiocrinus semperi and Hudiocrinus gaponicus the first 
pinnule is on the fourth joint after the radial. This would correspond to the second 
brachial of a ten-armed Crinoid, but it is really the fourth brachial in Eudiocrinus. 
Lastly, in Perrier’s Kudiocrinus atlanticus * the first pinnule is on the fifth brachial, which 
corresponds to the third brachial of an Antedon. 
The well-known genus Rhizocrinus resembles Hudiocrinus indivisus in the syzygial 
union of the first two joints beyond the primary radials (Pl. X. figs. 1, 2, 6-8, 20). 
They have generally been called the second and third radials ; and there is some ground 
for this in the case of Rhizocrinus lofotensis, as they are considerably broader than all the 
joints which follow them except the first (Pl. LX. figs. 1,2). But in Rhizocrinus rawsoni 
(Pl. IX. fig. 3; Pl. LIII. fig. 7) they are not much larger than the four following joints, which 
contribute with them to support the visceral mass (Pl. X. fig. 20); while the first pinnule 
is on the last of these, 7.e., on the sixth joint above the calyx (PI. IX. fig. 3; Pl. X. fig. 20). 
Considering the evidence afforded by Hudiocrinus, I think, however, that it will be more 
consistent to describe Rhizocrinus as having only one radial; while the first pinnule 
would then be on the sixth (Rhizocrinus rawsoni) or on the eighth brachial (Rhizocrinus 
lofotensis). The terms second and third radials would then be used only in those cases 
where there are ten or more arms, owing to the third radials and more or fewer of the 
1 Op. cit.,p.5. Seealso the genus Actinometra, Trans. Linn. Soc. Lond. (Zool.), ser. 2, vol. i. pp. 20-25, 1883 ; Zittel’s 
Palontologie, t. i. p. 339; de Loriol, Paléont. Frang. Terr. Jurass., t. xi. p. 15; Wachsmuth, Revision, part ii. pp. 9, 10. 
2 Budiocrinus and Atelecrinus, Journ. Linn. Soc. (Zool.), vol. xvi. p. 495, 1882. 
3 Sur des Eudiocrinus de Y Atlantique et sur la nature de la faune des grandes profondeurs, Comztes Rendus, t. 
xevi. No. 11, p. 726. 
