206 Mr. F. A. Bather on British Fossil Crinodds : 
RESTRICTION OF THE GENUS. 
Having determined the type species of the genus, we have 
now to consider various forms that have at different times 
been confused with Cyathocrinus. 
It is unnecessary to say more about the separation of Pote- 
riocrinus from Cyathocrinus, since it differs not only in the 
anal area but in the possession of pinnules. 
Parisoerinus has arms like Cyathoerinus, but an anal area 
like Potertoertnus ; hence there is no real reason for confusing 
the two as has often been done. 
J. Hall * extended the diagnosis of Cyathocrinus to include 
forms with a small quadrangular radianal. These forms, 
however, differ in other respects, besides the presence of a 
radianal, from Cyathocrinus, and doubtless belong to quite a 
different family—the Decadocrinide. In America such forms 
are represented by Barycrinus and Vasocrinus: in England 
it is the Silurian Lotryocrinus that has been labelled Cyatho- 
erinus tT; while a Carboniferous fossil that is probably a 
Barycrinus appears to have been considered a Polertoerinus. 
De Koninck and Le Honf gave a diagram of Cyatho- 
crinus in which the anal a was represented as pentagonal 
and as supporting two small hexagonal plates. ‘This was 
probably a mere slip, for neither in C. planus nor in C. 
mammillaris, the only species described by them, has the anal 
« that shape. Some specimens of C. multibrachiatus from 
the Keokuk group of North America, that are in the British 
Museum, appear to have an anal # of this shape, but it is net 
typical of the genus. In fact the diagram given by De 
Koninek and Le Hon resembles, in this respect at least, that 
ot Ottawacrinus alone among the Inadunata. They also 
give, under the head of Cyathocrinus, a diagram of the 
anal area of a Permian species, of which all we can say is 
that it certainly is not a Cyathocrinus. 
The Austins (op. edt. p. 66), in reviewing the species 
ascribed by different authors to this genus, said, * Not one of 
the so-called Cyathocrint of Murchison’s Silurian System 
properly belong to the genus.” ‘This is perfectly true: it 
has long been known that C. tuberculatus is a Taxocrinus, 
that C. pyriformis (sic) is an Ichthyocrinus, aud that €. 
rugosus 1s a Crotalocrinus; in fact these corrections were 
made when the plates were reprinted to illustrate Murchison’s 
* Rep. Geol. Surv. Iowa, vol. i. part ii. p. 622 (1858). 
+ “Brit. Foss. Crin., Vv. Ann. & Mag. Nat. Hist. ser. 6, vol. vii. 
p. 395, May 1891; and VJ., p. 189, antea. 
{ ‘ Recherches sur les Crinoides &c.,’ pp. 79 et sqg. (1854). 
