243 
The genus Poteriocrinus was established by Miller in 
1821, and in the systematic arrangement of the Crinoidea 
which he then proposed, stood as the representative genus 
of an entire section, in consequence of certain peculiarities 
presented by the plates, which compose the calyx or body- 
cup of the animal, being regarded by him as constituting 
characters of primary value in classification. Subsequent 
investie^ation havinn^ shown that these details of structure 
were not associated with other special features, and pre- 
sented no distinctions which would warrant their employ- 
ment for such a purpose, this arbitrary and erroneous view 
has long since been discarded; and it will not, therefore, be 
needful to encumber the following remarks with further 
allusions upon the subject. 
The present paper will be confined solel}^ to the con- 
sideration of British Carboniferous forms of Poteriocrinus, 
leaving for some future occasion a review of the extreme 
limits of the variability of the genus, as indicated by its 
distribution in time and space. 
I. — A List of British Carboniferous Crinoids ivhich have 
been assigned by various Authors to Poteriocrinus, 
Miller. 
The following species have been described as belonging 
to the genus Poteriocrinus : — 
By Miller^ P. crassus, 
P. tenuis. 
By Phillips^ P. impressus. 
P. conicus. 
P. granulosus. 
P? nob His. 
P? Kgertoni. 
(1) Miller — A Natm-al Uistory of tho Crinoidea. 
(2) Phillips— Geology of Yorkshire. Part II. 
