30 PLATTCRINID^. PLATYCRINITES. 



in which the rays have been found attached, while in those with elongated tubular 

 mouths they have been observed in all but a perfect state of preservation. The same 

 remark applies equally to the Actinocrinites as it does to the Phitj/crinites. 



The Column. — As no portion of the pedicle of tliis species has been discovered, it is 

 impossible to offer an opinion on its structure, beyond observing that the articidating 

 striae on the dorso-central plate are such as to prove that the upper portion was circidar. 

 Whether the same changes of column were general in the animals with unobtrusive 

 mouths as in the tyjiical species, no satisfactory opinion can be formed, so in the absence 

 of all evidence to shew the nature of the columnar structure, it woidd be premature to 

 speculate on its probable form. 



The Base of Attachment — unascertained. 



Though we have in a previous page expressed our behef that this portion of the tyj^ical 

 and other species remains undiscovered, we by no means intend to imply that the basal 

 portions of columns of Platijcrinites, with the calcareous fibres by which they attached 

 themselves to the rocky bed of the ocean, have not been obtained, but merely to guard 

 against the error of assignhig the base of one animal to another, to wMch it may not 

 properly belong. 



Many fragments which exhibit the exuded calcareous matter, and which is sometimes 

 prolonged into lengthened fibres of attachment, were referred by MiUer to the P. Icevis ; 

 but they are as likely to appertain to one species as another, for they have never been 

 seen attached to a perfect specimen of any known species. 



The strildng difference in the structure of the valvate mouth of this species, when 

 compared with the elongated oral tube of the P. Icevis, is sufficiently characteristic to 

 justify its removal from the genus in Avhich we have placed it. But for our reluctance 

 to add to the already superabundant nomenclature of science, we should not hesitate so to 

 remove it into oiu- proposed genus Centrocrinus, and to constitute it the typical species. 



6. Species. Platycrinites trigintidactylus. (Austin. J 



Definition. — Body globose, dorso-central plate pentagonal and undivided, with a 

 circular central perforation communicating with the columnar canal. Perisomic plates 

 five, broad, smooth, and slightly orbicular on their lower edges. Mouth central and 

 proboscidial. Basal ray joints five, subdivisions thirty. Column circular in its upper 

 portion, but eUiptical towards the base. 



