REPORT ON THE CRINOIDEA. 211 



a local collector " a small worn and rounded fossil, which seemed to bo the cup of a 

 Crinoid allied to Holopus." 



Prof. Moseley tells me that he tbinks it wfis a recent specimen in the dry state ; but 

 since it has unfortunately been lost, I am unable to say anything as to its nature. 



B. On the Systematic Position of Holopus. 



For some time after the publication of d'Orbigny's original descrijition 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, Eoemer ^ made the genus the type of a new family, Holopocrinidse ; 

 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 Holoinis might be merely a larval form, 

 destined eventually to become detached and to imdergo further transformations. He 

 added " Die Kiirze der Saule, die keilformigen Armglieder mit einfachen Pinnulen sprechen 

 an meisten flir die Comatulafamilie." The latter character, however, is absolutely 

 worthless as a generic distinction, many Comatulse having discoidal or saucer-shaped arm- 

 joints like those of Pentacrinus and Ajnocriims, while all the Neocrinoids have simple 

 pinnules. The first peculiarity mentioned hj 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 Cyatliidiwn by Steenstrup,' who spoke of it as like Eugeniacrinus, but without a 

 stem. In Theil ii. of the Lethsea Geognostica, Eoemer made it the type of a sejjarate family 

 Cyathidiocrinidse, which he placed next to the Holopocrinidse ; but in Theil v. he refers 

 to it as belonging to the Poteriocrinidse, together with Eugeniacrinus and Taxocrinus. 



Between Holopus and Steenstrup's Cyatliidiwm from the Faxoe Chalk there is 

 certainly a very close analogy, though there are a few well marked difi'erences. Apart 

 from the bud-like peculiarities of growth presented by Cyathidium, 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 Lethaea Geognostica, Theil. ii. pp. 226, 227. 2 Encriniden, p. 186. 



^ Anit Bericht ii. d- 24 Vtrsamml. deutsch. Kuturf. und Aerzte in Kiel, 1846, puLli.sbeJ 1847, p. 15. 



