REPORT ON THE CRINOIDEA. 249 
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qui forme un grand évasement obconique ou caliciforme, ce qui donne 4 notre Crinoide 
de la ressemblance avec le genres fossiles Apiocrinus et Bourgueticrinus. Cette extremité 
nest done pas autre chose que le sommet de la tige qui s’élargit suecessivement.” Sars 
considered the summit therefore as an enlarged uppermost stem-joint analogous to the 
centro-dorsal of the Comatule. He was unable to resolve it into any component parts 
by treating it with alkalies; and it is consequently not surprising that he was led to 
regard the whole subradial portion of the calyx as composed of but one single piece. In 
fact he was never able to separate this piece from the radials or the radials from one 
another, the existence of these plates being only indicated on the outside of the calyx by 
very faint sutural lines, occasionally rendered more distinct by slight furrows. 
It never seems to have struck him, however, that there might be basal plates below 
the radials which were similarly, but more closely anchylosed ; and he was led to consider 
the basals as fused, lke those of Comatulz, into a kind of rosette. This circular plate 
(Pl. VIIla. figs. 6, 7; Pl. X. figs. 1, 4—br) “est située & Vintérieur dans l’espace central 
laissé en dedans de l’'anneau formé par l’adhésion des premiers radiales ;”! but Sars was 
unable to isolate it, owing to its very close adherence to the first radials. 
It has been pointed out that Rhizocrinus was dredged by Pourtalés in 1868 before he 
had heard of its discovery by Sars; and the condition of his specimens was fortunately 
such that he was able to describe the calyx as “‘ composed of a cycle of elongated basal 
(pelvic) pieces, followed by the much shorter first radials (costals) alternating with them. 
These pieces are all so intimately connected with each other that the sutures are seen 
with difficulty.”” This account seems to have escaped the notice of Sir Wyville Thomson; 
for in his description of the ‘‘ Porcupine ” Crinoids’ he stated that “in Rhzzocrinus the basal 
series of plates of the cup are not distinguishable. They are masked in a closed ring at 
the top of the stem.” He did not, however, entirely accept Sars’s view of the composi- 
tion of the calyx; for he went on to say that ‘‘ whether the ring be composed of the 
fused basals alone, or of an upper stem-joint with the basals within it forming a rosette 
as in the calyx of Antedon, is a question which can only be solved by a careful tracing 
of successive stages of development.” The relatively large specimens which were dredged 
by the “ Porcupine” in 862 fathoms off Cape Clear, show the interbasal sutures very 
clearly ; and though they were referred at the time to Rhizocrinus lofotensis, they really 
belong to the Caribbean species Rhizocrinus rawsoni, larger specimens of which were 
obtained by the “ Hassler” off Barbados in 1871, and described by Pourtalés in 1874. 
These, like the “ Porcupine” specimens and the Gulf Stream variety of Rhizocrinus 
lofotensis, also showed distinct interbasal sutures. Pourtalés was therefore led to 
dissent from Sars’s description of the calyx in this genus, and to repeat more emphatically 
his own previous statements concerning the existence of long but closely united basals.* 
1 Crinoides vivants, p. 12. 2 Bull. Mus. Comp. Zool., vol. i. p. 129. 
3 Proc. Roy. Soc. Edin., vol. vii., 1872, p. 770. 4 Mem. Mus. Comp. Zodl., No. 8, pp. 28, 29. 
(ZOOL. CHALL. EXP.—PART XXx1.—1884.) Ti 32 
