POTERIOCRINID.E PENTACRINUS. 115 



articulating surface of the joints, Mr. Miller had recourse to certain columns found 

 in the lias, and which he referred to this species, but which we consider incorrect, for 

 assuredly none of the fossil specimens can be properly considered as identical with the 

 recent pentacrinus. 



The Auxiliary Side Arms or Claspers occur in circles of five, at intervals along 

 the column, the intervening spaces varying in extent, but irregularl}' increasing from 

 the summit to the base, that is, assuming the same arrangement, obtains in its lower 

 portion as we find it in that part which we have had opportunities of examining. 



The columnar joints from which the claspers proceed have in each retiring angle a 

 slight depression occasioned by the absence of the thin contracted membrance which is 

 said to envelope the column of the living animal. These are the points of adhesion 

 for the claspers, which are not so deeply inserted, or grafted into the column as they 

 are in the Poteriocrines and some other genera of still greater antiquity. The claspers 

 being perforated and placed in the deep sinuosities between the angles of the column, 

 are, from their proximity to the central canal readily supplied with the secretions 

 necessary for their support. This arrangement is equivalent to that noticed in some of 

 the older crinoids, the same end however being obtained by different means, but in 

 both cases the claspers are brought within a gi^en distance of the central axis, 

 an arrangement perhaps necessary in order to facilitate the supply of calcareous matter 

 for the construction of the joints, as well as of vivifj'ing juices to maintain the part in 

 full vigour. 



The newly formed claspers are, near the body of the animal, exceedingly small, and 

 occur at very brief intervals around the column. Those which are fully developed 

 consist of about forty joints each, which are shorter near the column than they are 

 towards their terminal points. The claspers are circular or nearly so, and are capable 

 of motion in every direction, either laterally or perpendicularly to the axis of the 

 column. 



There can be no reasonable doubt as to the P. Crput Meduste being in its living state 

 permanently attached to the bed of the ocean by an indurated base, all the specimens 

 hitherto obtained having been evidently broken off by mechanical violence, the columns 

 presenting at the fractured parts proof tliat considerable efforts had been exerted to 

 separate them from the lower portions, which stdl remained adhering to the sea bottom. 

 Some years since, Mr. J. Tobin, who had an opportunity of examining a specimen 

 which had just been drawn up from the sea, made the following observation respecting 

 it — " It was brought to me so fresh out of the sea that at the bottom, where it plainly 

 appeared to have been broken of! from the rock to wliich it was fixed, the blood" (the 

 fluid which passes through the columnar canal,) " was actually oozing from the 



