REPORT ON THE CRINOIDEA. 115} 
extremities they are well adapted to retain their hold. The stem itself passes slowly 
from a rigid vertical attitude to a curved or even drooping position.” 
The shape of the nodal joints is markedly different from that of the internodal joints 
which separate them. They are not only somewhat higher (Pl. XIX. figs. 3, 4; 
PL MXVIC tetas Pi MXVIE fig. 1; Pls XXXV., XXXVI; PL XXXIX. fig, 3; 
PL XLT figss1 55,15; PE XDI; Pl. XLV. fig. 6; Pl. XLVIL figs. 1, 2), but the outline 
of the upper non-syzygial face is different from that of an internodal joint. (Compare 
Pl. XXXIX. figs. 4,8; Pl. XLI. figs. 2, 3, 6,7, 16,17; Pl. XLV. figs 2,4; Pl XLVI. 
figs. 4, 5, 8,9; Pl. LI. figs. 9,10; Pl. LIII. figs. 3, 4.) In the recent Pentacrinus and 
Metacrinus every nodal joint is united by syzygy to the top joint of the next internode 
below. I propose to give the name “infra-nodal” to this joint, which is really the 
hypozygal of the syzygial pair (Pl. XXII. figs. 19-22; Pl. XXVI. figs. 12-16; Pl. XXX. 
figs, 26-29; Pl. XXXVII. figs. 5-8, 19-22; Pl. XX XIX. figs. 3-7; Pl. XLV. figs. 3-5; 
Pl. XLVIL. figs. 3,7; Pl. L. figs. 19-22; Pl. LIIL. figs. 3, 5). The apposed faces of 
these two joints are much more distinctly stellate than are those of the remaining stem- 
joints, the re-entering angles of the star being the points of attachment of the cirri, 
and the syzygial surfaces of the mature joints are almost smooth and devoid of any 
markings whatever. 
The syzygial union of two stem-joints is effected, just as it is in the rays and arms, 
by short fibrils of connective tissue, very numerous and closely set. They form a kind 
of “‘ cement substance,” as it was formerly called, which is connected at its ends with the 
organic basis interpenetrating the calcareous network of the stem-joints, just as the 
“cement-substance” of the arm-syzygies is connected with the organic basis of the 
brachials. But these fibrils are absolutely distinct from those of the five long ligamentous 
bundles which occupy the internodes. The latter are often spoken of as tendons, and 
have been wrongly described as extending throughout the whole length of the stem. 
Were this really the case, it is difficult to see how the stem could break across at the 
syzygies so easily as it does; for there would be no reason why the five tendons should 
be weaker at these points than at anywhere else in the internodes, while the loose ends 
of the tendons should appear at the surfaces of fracture, just as they do where an inter- 
node is forcibly broken across. But this is not the case ; when the stem is decalcified the 
joints separate very readily along the lines of syzygy, and it is then apparent that the 
five tendons run from the lower portion of each infra-nodal joint down into the upper 
portion of the next nodal joint below it. They end within these two joints, just as do 
the ligaments which connect two brachials, terminating either in looped extremities or 
else passing into the connective tissue plexus which forms the substance of all the joimts 
whether of arm or stem. 
The various internodal joints are, as it were, strung upon these tendons, which are 
thus not continuous, but divided up into lengths, each corresponding to an internode ; 
