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II. Notes on some Echinodermata from the Mountain-limestone, Etc.

Published online by Cambridge University Press:  01 May 2009

John Rofe
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Extract

Several years since, when collecting Mountain-limestone fossils on the borders of Lancashire and Yorkshire, I found some specimens of Actinocrinus which appeared to have internal channels from the base of the arms towards the summit of the dome. Not having seen such channels noticed by any author, I showed some of the specimens to Mr. Salter, then of the Geological Survey, who suggested that they probably might be analogues of the aquiferous channels found in recent Echinoderms; and he advised me to follow up the subject, and ascertain if such passages were to be found in other Crinoidea occurring in these rocks. His advice has been followed, and a large collection of specimens, some in good preservation and others weathered, has been made, which I have had the advantage of collating with a series from the same district collected by Mr. James Parker of the Manchester Museum; and upon examination they give the following results, some of which, though probably of no great importance in themselves, may serve to illustrate some doubtful points in the organization of this confessedly obscure Order of the Animal Kingdom.

Type
Original Articles
Information
Geological Magazine , Volume 2 , Issue 12 , June 1865 , pp. 245 - 252
Copyright
Copyright © Cambridge University Press 1865

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References

page 245 note * Cyclopædia of Anatomy and Physiology, vol. ii. p, 40, and vol. iv. p. 332.Google Scholar

page 246 note * Messrs. Austin, when describing Cyathocrinus, say—‘The ray-bearing plates are perforated low down from their upper edges, for the passage of the muscles of the rays. A deep groove runs from each perforation to the summit of each plate, which is prolonged considerably beyond the point of attachment for the rays, and is in-arched, so as to partially cover in the vertex. This is particularly conspicuous in C. geometricus, and appears to be very common in Crinoids of this genus“

page 247 note * Phillips, in his ‘Geology of Yorkshire’ (Part II., PL IV. fig. 2,5), gives a diagram of one set of radial plates in which the ovarian openings, under the base of the arms, are clearly indicated.

* In well-preserved specimens of plates of the Crinoidea, and probably of all the Echinodermata, the face of the joints of the plates is minutely wrinkled or corrugated, which will at once distinguish true joints from fractures. By this means the doubt as to the construction of the base of the Platycrinus has been removed, a divided base having been found showing the wrinkled structure on the face of the joints. As these bases are generally found whole, and very rarely in detached plates, most probably M. de Koninck's view, that in full-grown specimens they are auchylosed into one, is correct.

page 248 note * Cyclopaedia of Anatomy and Physiology, vol. ii. p, 40, and vol. iv. p. 332.