178 SYNOPSIS OF THE CHARACTERS OF THE 



The specimens which have occurred are very imperfect, and difficultly recognizable ; they approach nearer 

 to the Devonian than to the mountain limestone specimens. 



POTERIOCRINUS GRACILIS. M'Coy. (PI. XXV. figs. 11 tO 14). 



Sp. Ck. — Body, measured from the pelvis to the scapulae, nearly twice as long as wide ; smooth, length of 

 the arm-joint twice its thickness. 



This is closely allied to the P. tenuis, Mill., but is much more slender, and the plates of the body pro- 

 portionably longer; the arm-joint is also much shorter; the column is formed of round, equal, thin joints, with a 

 broad surface of articulation radiatingly striated ; the proboscis is very long, and from the strong, radiating, muscu- 

 lar ridges, assumes a beautifully stellated appearance. Length of body five lines, width three and a half lines. 



POTERIOCRINUS IMPRESSUS. Phil. 

 Poteriocrinus impressus. Phil. Geo!. York. 

 Sp. Ch. — Conical, smootli, angles of the plates impressed ; pelvis very small, supporting five pentagonal 

 first costals, which are broader than long. 



This large species is distinguished by having the angles of the second costals, scapular and interscapular 

 plates deeply indented ; the scapular articulation occupies about two-thirds the width of the plate. 



Taxocrinus. Phil. 



Isocrinus. Phil, (not Von Meyer) Bladocrinus. Aitst. (not Agas). 



Gen. Ch. — Column enlarging towards the pelvis, pelvis of five very small plates; costals five; the joints 

 are equal and similar, from those to the first cuneiform arm-joint; arms and hands very long. 



Taxocrinus macrodactylus. Phil. 



Cyathocrinus macrodactylus. Pkil. Geol. York Isocrinus macrodactylus. Phil. Pal. Fos. 



Sp. Ch. — Pelvis supporting five pentagonal, and five quadrangular, costal plates, bearing five quadrangular 

 scapulae, each supporting one cuneiform ami-joint, from each of which proceed twohandsof five joints dividing 

 into numerous fingers ; surface smooth. 



This species occurs of considerable size, but very imperfectly preserved ; I have deviated a little from Pro- 

 fessor Phillips in my view of the plates of the body, hands, and arms. 



Taxocrinus polydactylus. M'Coy. (PI. XXVI. fig. 7)- 



Sp. Ch. — Column of numerous round, unequal joints; about twenty of them at the summit suddenly in- 

 crease in diameter, but become very thin, and are perfectly equal ; those support five pentagonal, pelvic (first 

 costal ?) joints ; these support five heptagonal scapula2(?), each supporting a series of five or si.x equal, cylindrical 

 joints, terminating in a cuneiform joint, bearing two hands divided into five or more fingers; surface smooth. 



The complex genus, Taxocrinus, now contains a considerable number of well-marked species, of which 

 that before us is not the least curious ; the upper joints of the column are suddenly dilated, as we see in 

 Apiocrinus, forming an enlarged alimentary cavity, and leaving us in doubt as to the true pelvis of the 

 genus ; the supra-columnar joints are five, pentagonal, and support five, large, heptagonal plates, which, perhaps, it 

 is safer to call scapula than any thing else ; from these to the first cuneiform joint, as we see in the other Tax- 

 ocrini, the joints are equal and similar; this joint supports two hands, having each a great number of fingers. 

 The surface Is smooth; diameter of the body at supra-columnar joints six lines. Length from the supra-colum- 

 nar joint to the tip of the fingers, as far as known, three inches and a half. 



Cyathocrinus. Mill. 



Gen. Ch. — Pelvis of five pentagonal plates; supporting five costals; column round or pentagonal; articu- 

 lating surfaces radiated. 



