206 Mr. F. A. liatlier on British Fossil Criiiotds : 



Restriction of the Genus. 



Having determined the type species of tlie genus, we liave 

 now to consider various forms that have at different times 

 been confused with Cyalhncrinus. 



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. 



Parisocrinvs has arms like Cyathocrinus^ but an anal area 

 like Poteriocrinus ; hence there is no real reason for confusing 

 the two as has often been done. 



J. Hall * extended the diagnosis of Cyaihocrinus to include 

 forms with a small quadrangular radianal. These forms, 

 ho^Yever, differ in other respects, besides the presence of a 

 radianal, from CyatJiocrinus, and doubtless belong to quite a 

 different family — the Decadocrinidas. In America such forms 

 are represented by Barycrinus and Vasocrinus: in England 

 it is the Silurian Boiryocrinus that has been labelled Cyatho- 

 crinus^ ] while a Carboniferous fossil that is probably a 

 Barycrinus appears to have been considered a Poteriocrinus. 



De Koninck and Le Hon X gave a diagram of Cyaiho- 

 crinus in which the anal x 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. 

 mammillarisj the only species described by them, has the anal 

 X that shape. Some specimens of C multilrachiatus from 

 the Keokuk group of North America, that are in the British 

 Museum, appear to have an anal x of this shape, but it is not 

 typical of the genus. In fact the diagram given by De 

 Koninck and Le Hon resembles, in this respect at least, that 

 of Ottaicacrinus alone among the Inadunata. They also 

 give, under the head of Cyaihocrinus, a diagram of the 

 anal area of a Permian species, of which all we can say is 

 that it certainly is not a Cyaihocrinus. 



The Austins {op. cit. p. 66), in reviewing the species 

 ascribed by different authors to this genus, said, " Not one of 

 the so-called Cyathocrim of Murchison's Silurian System 

 projjcrly belong to the genus." This is perfectly true : it 

 has long been known that C. tuberculatus is a Taxocrinus, 

 that C. pyri/ormts {sic) is an IchthyocrinuSj and that C. 

 rugosus is a Grotalocrinus ; in fact these corrections were 

 made when the plates were reprinted to illustrate Murchison's 



* Eep. Geol. Surv. Iowa, vol. i. part ii. p. 622 (^1858). 

 t " Brit. Foss. Criu., \'.," Aim. ^: Mag. Nat. Hist. ser. 0, vol. vii. 

 p. 39"), May 1801 ; and VI., p. ISO, antea. 



\ ' Ivcclierclies sur Ics Criuoidos \c.,' pp. 70 et f^ijij. (1854). 



