HISTORICAL. 17 
B. Stylida, Crinoids with a jointed column. 
a. The tegmen formed of a skin. 
Pentacrinide, Apiocrinide, Eugeniacrinide, Encrinide, Cupressocrinide, Cya- 
thocrinide. 
b. The ventral surface covered by heavy plates, immovably united. 
Poteriocrinide, Rhodocrinide, Platycrinide, Actinocrinide, Melocrinide, 
Ctenocrinide, Sagenocrinide, Anthocrinide. 
ce. The arms imperfectly developed. 
Haplocrinide and Gastrocomide. 
Roemer’s families are natural groups, except his Cyathocrinide, among 
which he united a number of widely different forms. But this is partly due 
to Miller, who had included with Cyathocrinus forms which were afterwards 
referred even to different orders. Roemer, believing that Miller’s typical 
species, Cyathocrinus planus was a Poteriocrinus, made his second species 
Cyathocrinus tuberculatus, which Phillips in 1843 had made the type of 
Taxocrinus, the type of Cyathocrinus. 
Together with the Classification was published Roemer’s classical memoir 
on the Cystidea and Blastoidea, of which especially that of the latter fur- 
nished most valuable additions to our knowledge of the morphology of that 
group. 
In 1845 appeared the Memoir of Leopold von Buch on the Cystidea. He 
gives excellent descriptions of several genera, and places the group at equal 
rank with the Blastoidea and Crinoidea. 
De Koninck and Le Hon, in 1853,* described a number of new species 
from the mountain limestone of Belgium, and proposed certain changes in 
the terminology of the calyx plates. The proximal ring of plates he calls 
“basals,”’ whether the species is monocyclic or dicyclic; those of the second 
ring in dicyclic forms “ sous-radiales.” The radials comprise all plates up to 
the first axillary; and the succeeding plates of the rays, when parts of the 
calyx, are “articles brachiaux,”’ otherwise arm plates. The term “ inter- 
radiales” is applied only to the plates of the four regular sides; those of 
the posterior side are “ piéces anales.” 
Another classification was brought out by Pictet, in 1857,¢ who divided 
the Crinoids into nine families. The first and ninth of his families contain 
almost exclusively Neozoic forms. The former embraces the Comatule and 
Marsupites, to which was added the Paleozoic Astylocrinus ( Agassizocrinus) 
; 
* Recherches sur les Crinoides du Terrain Carbonifere de la Belgique. 
+ Traité de Paléontologie, par F. J. Pictet, Paris, 1857, Tom. V., pp. 278-3465. 
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