rLATYCRINID.Ti:. PLATYCRINUS. 35 



Tlie lines of the larger granulac when viewed from the base of the rays, and in the 

 direction of the column, present well defined lozenge-shaped figures, which are 

 extremely neat and beautiful. 



The Meso-Plates.^ — These plates do not extend below the basal joints of the ra3's. 

 They are irregularly lozenge shaped, and the lines of granuloe with which they are 

 ornamented conform to the outward form of the plates. 



The Abdominal Plates — Irregularly hexagonal, and studded with granulse. 



The Proboscis — Is central and elongated, and the plates which envelope the tube, 

 are granulated in the same manner as the abdominal plates. 



The Rays. — In this species the rays amount to thirty five, and differ from the other 

 Platycrini in being single jointed throughout their whole length. This peculiarity may 

 be considered by some observers as sufficient to remove the granulalus from the genus 

 in which we have retained it. But as the rays are so very seldom found attached to any 

 of the fossil Crinoidea, we regard them as very questionable characters to found genera 

 on, and we therefore consider we are furthering the true ends of science by restraining the 

 number of genera, instead of extending them. If imperfect specimens of the granulatus 

 are examined an apparent irregularity in the number of rays may be observed, but which 

 irregularity does not in reality exist. It is necessary to notice this as some writers have 

 supposed that no dependance can be placed on the number of the rays in the diflerent 

 species of Crinoidea, so that any excess or deficiency in the reputed number which may 

 happen to occur in a broken or imperfect specimen, is at once placed to the account of 

 nature, who is accused of indulging in all sorts of fanciful unmeaning vagaries and un- 

 certainties. Nothing can be more fallacious than this mode of getting over a difficulty, 

 for the doctrine which teaches that Nature sometimes errs, but Philosophy never, may 

 be a convenient mode of disposing of a question which the latter is unable to solve. But 

 the doctrine is not sound, nor will it bear the test of examination. Occasional 

 irregularities may, and no doubt do occur, but they are comparatively so few that they 

 can scarcely be taken into account. In proof of this we can confidently assert, that out 

 of upwards of four hundred specimens of the superior portions of Crinoidea which we 

 have collected from the strata in which they occur, we ha\e not met with more than four 

 or five irregularities occasioned either by deficiency or excess. 



As in the generality of animals of this genus the rays are arranged in five groups, but 

 each group is in this species composed of seven divisions, as follows. A single basal 

 cuneiform joint articulates by radiating strice on to the excavation in each of the peri- 

 soniic ray bearing plates. This is succeeded by the first divisions, each of which is 



