1848. | AUSTIN ON THE CYSTIDEA. 291 
one of the Lycopod family, and is of course incompatible with the 
idea of this central portion being a true medulla; these plants must 
therefore be still further removed from any supposed phanero- 
gamic alliances. 
2. Observations on the Cyst1pEA of M. von Bucu, and the Cri- 
NOIDEA generally. By Tuomas Austin, Esq., F.G.S. 
Tue following observations are offered with the view to explain, and 
it is hoped make clear, some hitherto doubtful pomts as regards the 
Crinoidea and Cystidea, particularly the geological distribution of the 
last-mentioned family. 
In Baron von Buch’s Notice of a new family of Crinoidal Animals, 
which he has termed Cystcdea, published in No. 5 of the Journal of 
the Geological Society, and also in the more lengthened paper on this 
subject, a translation of which is given in the same number, some 
observations are made, which I humbly conceive-will not bear the 
test of close examination. At page 11 it is said, the Cystidea are di- 
stinguished ‘‘ by having the mouth constantly at the apex, and in the 
centre, which is rarely the case in the Crinoidea.”’ 
This observation appears to be correct, as far as our knowledge of 
the Cystidea extends. But the assertion respecting the situation of 
the mouth in the Crinoidea is unsupported by the evidence of the 
most perfect specimens hitherto obtained, for a great majority of 
species have the mouth placed centrically ; and the three or four species 
of Platycrinus alluded to as having excentrical mouths, are rather 
exceptions to the rule than the rule itself. An enumeration of the 
following species, all of which have centrical mouths, will sufficiently 
prove this fact :—Platycrinus levis, P. granulatus, P. elongatus, P. 
spinosus, P. trigintidactylus, P. antheliontes ; Actinocrinus levis, 
A. triacontadactylus, A. polydactylus, A. elephantinus, A. cata- 
phractus, A. Colei, A. aculeatus, A. levissimus, A. longispinosus ; Po- 
teriocrinus crassus, P. tenuis, P. granulosus, P. radiatus, P. rostra- 
tus, P. quinquangularis, P. plicatus, P. longidactylus, P. pentago- 
nus, &c. &e. This list could be greatly augmented, but the species 
enumerated seem fully sufficient. 
With respect to almost all the Crinoidea having a bilateral arrange- 
ment, a right and left side, nothing can be more certain than that 
this is the case, and that without reference to any inequality of the 
basal plates. In different genera we have all the gradations of dorso- 
central plates composed of one, and up to five pieces, but this latter 
number is never exceeded. The genus Platycrinus, in which the 
basal or dorso-central plate is undivided, contains some species with 
excentrical mouths, but in the majority it is centrical. Whether it 
is proper to retain species, which differ in this respect so materially 
from each other, in the same genus, is a question for consideration. 
In the second Part of the Journal, No. 5, page 22, M. von Buch 
observes, that the influence of the mouth upon the form and distri- 
bution of the plates is universal in all the Crinoidea; and that where 
the basal plates are not exactly similar in form or arrangement, the 
