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Proceedings of the Royal Society 
remarkable forms for which the sea of the Antilles is famous. 
However, although the “ Challenger ” was not there in person, on 
her return Sir Rawson Rawson most kindly and liberally placed 
the finest of his specimens at my disposal for examination and 
description ; and it is through his liberality that I now have it in 
my power to exhibit the very singular creature which is the sub- 
ject of these notes. In 1837 M. Alcide d’Orbigny described and 
figured in the “ Magasin de Zoologie,” under the name of Holopus , 
a new recent genus of fixed Crinoids ; and as the description of this 
distinguished palaeontologist indicated an undescribed form of great 
interest, it was speedily reproduced in the “ Annales des Sciences 
Naturelles” and in Wiegmann’s “Archiv.” 
The specimen described by D’Orbigny, which was for a long time 
unique, was brought from Martinique by M. Sander-Rang. It sub- 
sequently passed into the possession of M. D’Orbigny, who described 
it under the name of H. rangii. D’Orbigny’s account was very 
clear and intelligible, and his determination was fully borne out 
by his figures ; and in Bronn’s “ Classen und Ordnungen des Thier- 
Reichs,” published somewhere about 1861, the description and 
figures are repeated, and a distinct family, Holopidae, is adopted 
for the reception of the single species. It is very singular that 
in the “ Historie Naturelle des Zoophytes Echinodermes,” by 
Dujardin and Hupe, published as a volume of the “Suites k Buffon” 
in 1862, the authors express their opinion that Holopus is not a 
Crinoid, but some totally different thing, probably a Cirriped, and 
they profess to have been unable to find D’Orbigny’s specimen. 
At M. D’Orbigny’s death his whole museum was bought by the 
Jardin des Plantes, and in the year 1867, through the courtesy of 
M. Fischer, I had an opportunity of examining the original speci- 
men there; and although it was in a very dilapidated condition, 
I had no difficulty in satisfying myself that it was a true Crinoid 
of a very peculiar type. 
Professor Louis Agassiz called at Barbadoes in the “ Hassler ” 
in 1873, and he there saw a second specimen of Holopus in Sir 
Rawson Rawson’s collection. Professor Agassiz intended to have 
published a full description of the specimen, which was lent to him 
for that purpose by Sir Rawson Rawson, but he was prevented from 
doing so by failing health, and after his death the figures which 
