20 THE VOYAGE OF H.M.S. CHALLENGER. 
ends at the sixth node. This is due to the great length of the internodes in this species 
CPL VII fie. 3; Pl. XIX. fig. 1). 
Pentacrinus maclearanus presents exactly the opposite type of structure. There are 
only twelve nodes in the stem of the solitary individual obtained (Pl. XVI). But these 
all occur in a stem barely 40 mm. long, as there are never more than two, and generally 
only one internodal joint ; while the cirri cluster thickly round the stem, so that it has 
an appearance more like that of Hatracrinus briareus than is commonly met with in the 
Pentacrinide. It is noteworthy that in the last-named species the stem does not seem 
to have reached any great length, and that it sometimes tapered downwards.’ 
This peculiarity was also noticed by MM. Eudes-Deslongchamps in some stems 
belonging to a large colony of Pentacrinites which they discovered in the Great Oolite 
of Soliers, near Caen ;? while it is very characteristic of Millericrinus pratt: from the 
same horizon in Gloucestershire ;* and also of the Carboniferous Woodocrinus, certain 
Blastoids, and of the Silurian Glyptocystites, Plewrocystites, and other forms. The most 
remarkable instance of this in a fossil Crinoid, however, is that of the Lower Silurian 
Glyptocrinus schafferi of S. A. Miller,* for which he has recently established the new 
genus Pycnocrinus. In one specimen found by Miller the lower part of the stem was 
“wound around a Crinoid column of a distinct species, almost as neat as a thread can be 
wound upon a spool. The column gradually tapers as it coils, until it becomes so small 
as to be scarcely visible to the naked eye, the larger plates of the column which give it 
that banded appearance, or make it resemble a string of small spools, gradually diminish, 
and before the column terminates it becomes as smooth as a silken thread.” 
Two other species from the same locality at Cincinnati, Lichenocrinus dubius and 
Dendrocrinus navigiolum, were also found by Miller to have tapering stems. In the 
case of the former he infers that ‘‘the column was free and used to direct and guide 
the course of the animal through the water, and perform such other functions as were 
performed by the columns of other floating Crinoids, except that it was never used 
for purposes of attachment.” One must not, however, conclude at once, from the 
tapering condition of the stem in a fossil Crinoid, that the animal was free in its habits. 
In a young Lucalyptocrinus crassus, for example, which is figured by Hall,’ the stem 
tapers downwards very considerably, but is attached below by a spreading root. 
I have found a tapering stem in certain individuals belonging to six species of 
recent Pentacrinide, but it appears to be the exception rather than the rule, and is 
therefore entirely devoid of any systematic value. 
1 Encriniden, p. 271. 
2 Etudes sur les ¢tages Jurassiques inférieurs de la Normandie, Paris, 1864, p. 232. 
3 On some new or little known Jurassic Crinoids, Quart. Journ. Geol. Soc., vol. xxxvill. pp. 31-33, pl. 1. figs. 6-8, 
10-14. 
4 Description of four new Species and a new variety of Silurian Fossils, and remarks upon others, Journ. Cincinn. 
Soc. Nat. Hist., vol. iii., 1880, pl. vii. fig. 3, p. 2 (of separate copy). 
5 Twenty-eighth Annual Report of the New York State Museum of Natural History, Albany, 1879, pl. xvii fig. 5. 
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