REPORT ON THE CRINOIDEA. 201 
a local collector “a small worn and rounded fossil, which seemed to be the cup of a 
Crinoid allied to Holopus.” 
Prof. Moseley tells me that he thinks it was a recent specimen in the dry state; but 
since it has unfortunately been lost, | am unable to say anything as to its nature. 
B. On tHE Systematic Position oF Ho.oprus. 
For some time after the publication of d’Orbigny’s original description of Holopus 
the real nature of this remarkable type was more’ or less misunderstood, partly, perhaps, 
because the original specimen was tetramerous and not pentamerous like most Crinoids. 
Eventually, however, Roemer * made the genus the type of a new family, Holopocrinide ; 
though he did not characterise it more closely. This proceeding was objected to by 
Quenstedt” partly on account of the imperfection of our knowledge of the type, and 
partly because he considered it possible that Holopus might be merely a larval form, 
destined eventually to become detached and to undergo further transformations. He 
added ‘‘ Die Kiirze der Siule, die keilf6rmigen Armeglieder mit einfachen Pinnulen sprechen 
an meisten fiir die Comatulafamilie.” The latter character, however, is absolutely 
worthless as a generic distinction, many Comatulz having discoidal or saucer-shaped arm- 
joints like those of Pentacrinus and Apiocrinus, while all the Neocrinoids have simple 
pinnules. The first peculiarity mentioned by Quenstedt is founded on a misapprehension, 
for he considered the calyx to be formed of the axillary radials only, regarding the tube- 
like body-chamber as a stem. It exhibits no transverse segmentation, however, and has 
five articular facets on its upper edge, while it encloses the viscera ; and all these characters 
are totally foreign to the stem of a larval Crinoid, or indeed of any Crinoid whatever. 
In the year 1847 a remarkable new type of fossil Crinoid was described under the 
name of Cyathidium by Steenstrup,’ who spoke of it as like Hugeniacrinus, but without a 
stem. In Theil u1. of the Lethzea Geognostica, Roemer made it the type of a separate family 
Cyathidiocrinidz, which he placed next to the Holopocrinide ; but in Theil v. he refers 
to it as belonging to the Poteriocrinide, together with Eugeniacrinus and Taxocrinus. 
Between Holopus and Steenstrup’s Cyathidiwm from the Faxoe Chalk there is 
certainly a very close analogy, though there are a few well marked differences. Apart 
from the bud-like peculiarities of growth presented by Cyathidiwm, it has a more open 
cup, with relatively thinner walls than that of Holopus, Its appearance varies consider- 
ably in different individuals, being sometimes low and shallow, and in other cases longer 
and more tapering. 
The articular facets on its upper edge are much smaller than in Holopus, and their 
downward slope faces inwards instead of outwards, as in the recent form (PI. III. fig. 1), 
1 Lethza Geognostica, Theil. ii. pp. 226, 227. * Encriniden, p. 186. 
3 Amt. Bericht w. d. 24 Versamml. deutsch. Naturf. und Aerzte in Kiel, 1846, published 1847, p. 15. 
