The characters of Plicatocrinus are entirely different from those of any recent Crinoid,
though its calyx has a singular resemblance to those of young Pentacrinide. The
Eugeniacrinide are a less aberrant group; but though the symmetrical forms of Hugenia-
crinus appear to have a considerable resemblance to Rhizocrinus and Bathycrinus in the
structure of the lower part of the cup and in the distribution of the canal system, yet
such types as Phyllocrinus and the distorted Torynocrinus are altogether different from
any recent Crinoid.
The Apiocrinidee, represented by some doubtful species in the Lias, flourished exten-


eine NS ne FNE PMC Nts a? ane Fs “ 7 ‘ , a id an”.
i Hron . : A


‘


REPORT ON THE CRINOIDEA. 145


sively through the Jurassic period, and died out in the Lower Neocomian. Their place
was taken by the Bourgueticrinide, which were formerly associated with them into one
family. We have no certain evidence of the occurrence of the typical genus Bourgueti-
erinus in other than Cretaceous rocks; though stem-joints which have been referred to
this genus occur both in Jurassic and in Eocene deposits. It is not unlikely, however,
that they belong to Thiolliericrinus or to Rhizocrinus respectively. The latter genus,
which is represented by two living species, is probably exclusively confined to the
Tertiary rocks, except perhaps for the so-called Bourgueticrinus alabamensis from the
Cretaceous formation of Alabama, U.S.; and some of the stem-joints hitherto referred to
Rhizocrinus or to Bourgueticrinus may possibly belong to Bathycrinus, no calyx of
which has yet been found in the fossil state.
