292 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. | Mar. 22, 
mouth is invariably upon the side. ‘To illustrate this, the genus 
Actinocrinus is cited, and the figure of 4. amphora (Portlock’s Geol. 
of Londonderry, pl. 15. fig. 4 a) is selected as an example. 
From this view I must venture to dissent, and to assert, on the 
contrary, that in all known species of Actinocrinus the mouth is m- 
variably centrical,—and. further, that the specimens referred to are 
not true Actinocrini, from which they differ materially in the num- 
ber of lateral plates and other particulars ;—and that although the 
basal plates are similar in the two genera, the position and form of 
the mouth being widely different negatives the idea that the number 
and arrangement of the basal plates, as a necessary consequence, re- 
gulate the position of the mouth. 
So striking is the difference between the so-called Actinocrinus 
amphora and the true Actinocrini, both as regards the position of 
the mouth and the number of plates composing the calcareous skele- 
ton, that I have been induced to place the 4. amphora and three 
other species with excentrical mouths in a new genus, for which the 
Or 
has not been named. 
Extended observations do not support the opinion that the mouth 
is only centrical in those cases in which the cup is based upon per- 
fectly regular five-sided plates. On a close examination and com- 
parison it will be found that the form of the dorso-central plate has 
little or no relation to the position of the mouth. In support of this 
statement, it can be demonstrated that all the Platycrines before 
enumerated have the mouths placed centrically, as may be seen on 
reference to our Monograph on the Crinoidea, or to numerous speci- 
mens in the author’s cabinet, while the Platycrinus rugosus, P. 
mucronatus, and P. tuberculatus, with precisely the same formed 
dorso-central plates, have the mouths placed excentrically.—Again, 
in the genus Cyathocrinus, where the dorso-central plate is composed 
of five equal pieces, forming a pentagon, the mouth in some species 
is excentrical. The C. planus is a case in point, so that no reliance 
can be placed on the form of the basal plate as indicating the posi- 
tion of the mouth. ; 
Respecting the geological distribution of the fossils which M. von 
Buch has placed in the family Cystidea (but which had been pre- 
viously arranged in the family Sphzeronidee of Gray, vide ‘ Annals of 
Natural History,’ vol. x. p. 111), M. von Buch at page 40, 2nd 
Part of the ‘Geological Journal,’ No. 5, states that the Cystidea be- 
long unquestionably to the most ancient formation of the earth’s sur- 
face, to the Silurian strata of the Paleozoic period,—that nothing 
analogous to them has hitherto been met with in more recent forma- 
tions,—and that they form the extreme verge of an entire group of 
Radiaria, the Cariocrimus indicating the way im which the passage 
from Cystidea to Crinoidea may have taken place. 
M. E. de Verneuil appears to entertain similar views respecting 
the Cystidea. In the General View of the Palzeozoic Fauna of Russia, 
which forms the Introduction to the second volume of the work on 
