148 THE VOYAGE OF H.M.S. CHALLENGER. 



types from the group of tlie Neocrinoids, to which they have been already provisionally 

 referred by de Loriol. 



Both have uniserial arms, a symmetrical calyx, and no anal side ; while in 

 Marsupites, at any rate, the first radials were perforated by canals, and united to the 

 second by muscular joints. Interradial plates, however, are well developed in both 

 genera, especially in Uintacrinus. But the upper series of so-called interradial and 

 interdistichal or interaxillaiy plates are really parts of the radial system, and correspond 

 to the pinnules of free arms, as was pointed out by Meek. At the same time he noted 

 their unusual size, and the fact that they are united with each other and with the main 

 divisions of the rays for some distance up, so as to constitute a part of the walls of 

 the body.^ 



Schliiter,^ to whom Meek's remarks seem to have been unknown, speaks of this as a 

 possibility, but rejects it on account of the absence of a central canal in the suj^posed 

 pinnule-joints, and other less important reasons. I cannot help suspecting, however, 

 that the canal will be found, and that the plates in question are really the basal joints of 

 the large lower pinnules. He describes how these plates group themselves together in 

 double rows, the lowest of which " geht aus von dem zweiten Distichalgliede. Sie 

 besteht vieUeicht aus 9 Stiicken jederseits. Die folgende Doppelreihe, aus kleineren 

 Tiifelchen zusammengesetzt, nimmt ihren Anfang vom ftinften Stiicke liber dem 

 Axillare." The first pinnule being on the second brachial, the next on the same side 

 would Ije on the fourth ; but since the third is a syzygial or double joint, the fourth 

 brachial is primitively the fifth above the axillary ; while Schluter's figures ^ show that 

 the double row of interdistichal pieces which " nehmen ihren Anfang vom vierten 

 Distichale aus " are really the pinnules on the epizygals of the two thii'd brachials. There 

 are many species of recent Crinoids (Pentacrinus, Metacrinus, Actinometra) which have 

 large lower pinnules with the basal joints closely fitted together just as in Uintacrinus 

 (PL XXXVIII. ; PL XXXIX. fig. 1 ; PL XLIII. fig. 2 ; PL LII. fig. 1) ; so that the 

 supposed resemblance in this respect between Uintacrinus and the Palseocrinoids goes 

 for nothing. Apart from these two genera there are no Secondary Crinoids which could 

 by any possil)ility be referred to the Tessellata ; and this is still more em^jhatically the 

 case with the Tertiary and recent forms. It is true that the most striking characters of 

 the recent Thaumatocriaus (PL LVI. figs. 1-4) indicate an affinity to early Palaeozoic 

 types {ante, pp. 39-46) ; but, considering that Thaumatocrinus is a Comatula, it is 

 more than probable that this resemblance is not due to any genetic connection. 



Thus then I regard the Neocrinoids as constituting a group or subclass which is 

 distinctly marked ofl' from its Pala30zoic predecessors. These became extinct with the 

 Palseozoic epoch, like the Blastoids, Cystids, and Palsechinoids. The latter in fact 



1 Grinnel, Note on the genus Uintacrinus, Bull. U.S. Geol. and Geog. Siu'vey of tlie Territories, vol. ii., No. 4, p. 377. 

 ' Op. cit, p. 58. 3 Qp_ ^i(_^ xaf. iv. figs. 1, 3. 



