122 THREE CRUISES OF THE " BLAKE." 



until attention was again called to it by Pourtales 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, 

 ^ourgueticrinus, 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 Bourgueticrinidae are movable upon one another ; they 

 are not uniformly discoidal, like those of the Pentacrinidae, but 

 are strung as it were upon five tendons of variable length. 



Agassiz, who watched the movements of RMzocrhius Raio- 

 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. It 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, I could 

 see, without great effort of the imagination, the shoal of Lockport, 

 teeining with the raanj'- genera of crinoids which the geologists of New 

 York have rescued from that prolific sihu-ian 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 crinoids belonging to the genera Bathycrinus, 



