VILL. Cyathocrinus. 205 
sidered as a synonym of C. planus. There is therefore no 
difficulty in deciding what Miller meant by C. planus, and 
there should consequently be no difficulty in distinguishing 
the genus Cyathocrinus. 
Before leaving C. planus, however, it may be as well to 
correct a few mistakes made by the earlier writers, lest they 
should again prove cause of confusion. 
Miller’s erroneous ascription of cirri to the species has 
already been noted. With regard to the arms Miller wrote 
(p. 87), ‘they are all tentaculated at alternate sides, and 
resemble those of Pentacrinus Caput Meduse.”? Similarly 
the Austins, though they scouted Miller’s figure of the arms, 
remarked (p. 60), ‘‘The rays were no doubt tentaculated, 
although none of the specimens show the tentacula.” It is 
certain, however, that tentacula or pinnules are not present ° 
in this species. 
The Ashmolean specimen figured by Miller showed the base 
of the anal tube clearly ; Miller, however, merely said (p. 87), 
“‘ this [abdominal] integument is swollen out, and gives the 
specimen a singular appearance.” The Austins regarded 
this aperture as the mouth. De Koninck and Le ‘Hon * 
appear to have understood that it was connected with the 
anus; but neither they nor previous writers were aware that 
the opening was followed by an anal tube. The plates 
around the base of this tube were displayed by Miller in his 
dissected diagram, fig. 830. Wachsmuth and Springer, how- 
ever (Rev. it 81, ‘footnote 1) consider that “the four small 
plates, arranged in the figure in a half circle, are to represent 
the interradials (oral plates) [deltoids] in the dome, and not 
the plates of the ventral sac, as might be expected.” This 
cannot be right: the specimen, as proved by fig. 29, possessed 
no deltoids, while in both figures the letter 'T points to a 
larger and irregularly shaped plate which was most probably 
the madreporite. 
Miller distinctly (p. 87), and the Austins in more ambiguous 
language (p. 59), both stated that the articular facet of the 
radial was perforated. ‘l’o the question whether there are 
any species of Cyathocrinus that possess this character we 
shall recur later on; in the Carboniferous species C. planus, 
at any rate, there is no doubt that in the radial facet the 
axial canal is not separated from the ventral groove. 
* “Recherches sur les Crinoides du Terrain Carbonifére de la Belgique,’ 
Mém. Acad. Roy. Belgique, vol. xxviii. . 81: Brussels, 1854. 
Ann. & Mag. N. list. Ser. 6. Vol. ix. 15 
