122 THREE CRUISES OF THE “BLAKE.” 
until attention was again called to it by Pourtalés in 1871, 
and he showed the stout-stemmed specimens collected by the 
* Hassler ” off Barbados to be of a species distinct from the 
one previously described. 
The predecessors of Rhizocrinus were well represented in the 
lower tertiary, and go back to the cretaceous, where its ally, 
Bourgueticrinus, was very abundant. | 
In Rhizocrinus, spreading rootlets extend below the regular 
joints. By expansion at the ends or sides of these rootlets the 
animals attach themselves to any foreign body they happen to 
find in the deep ooze in which they become anchored ; when 
once fixed, they probably remain so for life. The stem joints 
of the Bourguetierinide are movable upon one another ; they 
are not uniformly discoidal, like those of the Pentacrinide, but 
are strung as it were upon five tendons of variable length. 
Agassiz, who watched the movements of Rhizocrinus Raw- 
soni, says : — 
“ When contracted, the pinnules are pressed against the arms, and 
the arms themselves shut against one another, so that the whole looks 
like a brush made up of a few long coarse twines. When the animal 
opens, the arms at first separate without bending, but gradually the tip 
of the arms bends outwards as the arms diverge more and more, and 
when fully expanded the crown has the appearance of a lily. I have 
not been able to detect any motion in the stem traceable to contraction, | 
though there is no stiffness in its bearing. When disturbed, the pin- 
nules of the arms first contract, the arms straighten themselves out, 
and the whole gradually and. slowly closes up. Tt was a very impres- 
sive sight for me to watch the movements of this creature, for it told 
not of its own way only, but at the same time afforded a glimpse into 
the countless ages of the past, when these crinoids, so rarely seen now- 
adays, formed a prominent feature of the animal kingdom. 1 could 
see, without great effort of the imagination, the shoal of Lockport, 
teeming with the many genera of crinoids which the geologists of New 
York have rescued from that prolifie silurian deposit, or recall the for- 
mation of my native country, in the hillsides of which, also among fos- 
sils indicating shoal-water beds, other crinoids abound, resembling still 
more closely those we find in these waters." 
The English, French, and Norwegian expeditions discovered 
also other stalked erinoids belonging: to the genera Bathycrinus, 
