326 BRIAREAN PENTACRINITE. 



to various kinds of Sertularia and Flustracea in the Cove 

 of Cork, and other parts of the coast of Ireland. 



It appears that Pentacrinites are alhed to the existing 

 family of star-fishes, and approach most nearly to the Coma- 

 tula; (See Miller's Crinoidea, PI. 1, and p. 127:) the bony 

 skeleton constitutes by far the largest portion of these ani- 

 mals. In the living species this bony framework is invested 

 with a gelatinous membrane, accompanied by a muscular 

 system, regulating the movements of every bone. Although^ 

 in the fossil species, these softer parts have perished, yet an 

 apparatus for muscular attachment exists on each individual 

 bone.* 



The calcareous joints which compose the fingers of the 

 P. Europaeus, together with their tentacula, are capable of 

 contraction and expansion in every direction ; at one time 

 spreading outwards, like the Petals of an open flower (PI. 

 52, Fig. 2,) and at another rolled inwards over the mouth, 

 like an unexpanded bud ; the office of these organs is to 

 seize and convey to the mouth its destined food. Thus the 

 habits of living animals illustrate the movements and man- 

 ner of life of the numerous extinct fossil members of this 

 great family, and afford an example of the vahdity of the 

 mode of argument, to which we are obliged to have recourse 

 in the consideration of extinct species of organic remains. 

 In this process we argue backwards, and from the mechan- 

 ical arrangements that pervade the solid portions of fossil 

 skeletons, infer the nature and functions of the muscles by 

 which motion was imparted to each bone. 



I shall select from the many fossil species of the Genus 

 Pentacrinite, that, which from the extraordinary number of 

 auxiliary side-arms, placed along its column, has been called 

 the Briarean Pentacrinite, and of which our figures (PI. 51. 



* See the tubercles and corrugations on the surfaces of the bones engraved 

 at PI. 52, Figs. 7, 9, 11, 13, 14, 15, IG, 17. 



