C R I N O I D E A. 



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These plates appear to have been secreted from 

 the edges of the joints, at the points of articulation 

 with each other ; and he mentions a specimen which, 

 having been injured, exhibited this secretion actually 

 going on in the form of little globules attached to 

 many of the joints at their articulations, and he sup- 

 poses that this animal, when injured in any part, 

 performed the restorative process by exuding the 

 matter in question in the manner just described. 

 These pedicles are found of various sizes, some 

 not exceeding a quarter of a line in diameter, others 

 being at least two inches ; sometimes a number are 

 found together, either attached to corals, shells, or 

 other hard bodies, or, as most frequently, to the rock 

 itself. This junction of the pedicles, in many speci- 

 mens, produces the appearance of a number of 

 columns emanating from one common root, but by 

 making a section they are all found to be separate 

 animals, as the columns may then be perceived to be 

 perfectly distinct from each other, passing through the 

 mass, each surrounded by a cone formed of concentric 

 laminae, which cones, by the exudation before men- 

 tioned, have, outwardly, become so intermingled with 

 each other, as to form apparently but one mass. 



The longest animal of this kind met with by this 

 gentleman, he describes as composed of 158 joints, 

 forming a column about ten inches in length, the cir- 

 cumference of which diminishes slightly above the 

 pedicle, but continues of the same size (viz. about an 

 inch) until it arrives at the upper part, where it ex- 

 pands to the extent of four or five inches. The seat 

 of the greatest motion appears to have been about the 

 centre of the column, which is shown by its increased 

 strength of articulation in that part, exhibited in the 

 radiating grooves being very deeply marked, whereas 

 in the upper and other parts, where but little motion 

 was required, these indentations are exceedingly 

 minute. This column is composed of rings which 

 are thicker at the circumference than at the centre, 

 each being perforated in that part with a round hole, 

 and thus the lenticular cavities formed by the juxta- 

 position of the plates are connected together. 



The head consists of the enlarged columns, to 

 which are attached five wedge-shaped joints, five- 

 inferior and five superior costal joints, and five bones 

 called scapulae, to which are articulated ten arms, 

 which are furnished at their sides with a number of 

 feelers, forming a sort of fringe. The upper or colum- 

 nar joint has five radiating elevated ridges upon its 

 upper surface, between which are the attachments of 

 the five wedge-shaped joints, which are triangular 

 and flattened at the lateral edges, being the points 

 where they are articulated with each other, having 

 two equal articulatory faces at their upper surfaces, 

 divided by an elevated ridge, above which the five 

 inferior costal joints are placed, which are also of a 

 triangular shape, and are connected with each other 

 by lateral attachments, and present a cavity above, 

 which receives the superior costal joints, which in like 

 manner receive the scapulae. It appears probable that 

 an intervening muscular organisation existed between 

 the articulating faces of the joints, from the wedge- 

 shaped ones upwards to the scapulae. There is also 

 a gradual approximation of their internal and external 

 edges, and this, joined to their circular arrangement, 

 produces a conical cavity with the apex downwards. 

 Mr. Pearse suggests that this was probably closed 

 above, as that of the pentacrinite, with an integument 

 composed of a membrane covered externally with scales 



of an angular form, forming the cavity of the stomach ; 

 between the wedge-shaped joints five canals are also 

 found passing from the lower part of the stomach, each 

 of which terminates in an opening on the external sur- 

 face, the mouth of which is marked either by a depres- 

 sion or an elongation which sometimes extends to the 

 distance of an eighth of an inch, which openings he 

 supposes to have been the mouths of the oviducts. 

 To the superior surfaces of the five scapulae are 

 attached the ten arms, which appear to have consisted 

 of at least forty or fifty joints, shaped like a horse- 

 shoe, which are articulated to each other, and gra- 

 dually diminish in size ; as they approach their upper 

 extremities a small perforation penetrates each joint, 

 as before described in the vertebral column, through 

 which foramina it is possible the vessels for their 

 nutriment, or the ligaments by which they were 

 attached to each other, had their passage. The arms 

 have also a groove running the whole length of their 

 inner surface, while the outward one is of a rounded 

 form, and to the holes of each joint of the arm is 

 attached a finger whose joints are at first round, but 

 afterwards grooved at their external edges, and which 

 are also perforated. Each arm when perfect must, 

 according to this description, have had from forty to 

 fifty fingers attached to its sides, placed alternately, 

 and thus presenting a fringed appearance. 



He names his first species Apiocrimtcs globosus from 

 its having the head in a very globose form. It is 

 shorter than the other two species, and the irregulari- 

 ties on the surfaces of the joints, which were probably 

 produced by muscular contractions, are very faintly 

 marked. 



The inter medius has the head elongated, with no- 

 corresponding lessening in the circumference, or thick- 

 ening of the joints,which are thin and deeply crenated, 

 and the muscular impressions, as in the globosus, but 

 faintly shown. 



The Elwigatus is distinguished by the head being 

 very greatly elongated in many specimens, tapering 

 down nearly to the centre of the column ; the plates 

 are also at least three times thicker than those of the 

 other two species. The column is also of much 

 greater length, without any corresponding diminution 

 of circumference. The development of the various 

 articulatory surfaces is also very strongly marked, and 

 the plates have a tendency to become more acute at 

 their edges, than in the other species. The radii on 

 the surfaces of the plates of the column are so slightly 

 marked as to be scarcely visible, and on each of the 

 surfaces of the joint a central depression is found, 

 which is occasioned by the joint becoming at once two- 

 thirds thinner at that place than the surrounding por- 

 tion. This is also seen slightly in the two other species. 



Such is a summary of the account given by Mr. 

 Ghanning Pearse, the whole of which deserves the 

 particular attention of all those who make organic 

 remains their study. 



The geological distribution of the Crinoidea is also 

 highly interesting. They occur in all the formations, 

 commencing with the transition limestone, in which 

 impressions and portions of these animals have been 

 found. Their great depot, however, is in the moun- 

 tain limestone, in which no fewer than twenty of those 

 described by Miller are found, together with many of 

 the new genera and species not known to him. They 

 are also abundant in the lias, in which, however, seve- 

 ral of the species found in the lower formations dis- 

 appear, and others of hitherto unknown genera occur. 



