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.