PALiEOZOIC ECHINODERMATA. 107 



Poteriocrinus crassimanus (M^Coy). 



Sp. Char, Column small, of thin circular joints ; supracolumnar 

 joint supporting five pentagonal first-costals, slightly wider 

 than long, between and above which rest five pentagonal sea- 

 pul(B about as long as the costals, but about one-third wider 

 than long, each of which supports one large cuneiform arm- 

 joint, wider than long, from each of which proceed two hands 

 of six joints each, thicker on alternate sides, the last joint 

 cuneiform and supporting two fingers of about thirty-five 

 joints, each wider than long ; costal and scapular plates ra- 

 diatingly marked at their margins. Length of cup 3^ lines, 

 width 6 lines, length of rays 2 inches. 



Of the arms visible one has but four joints, one has seven, and 

 the other three visible have six each. This species difi'ers from 

 the P. radiatus (Aust.) by the slighter radiation of the plates, the 

 greater proportional width of the cup, the articulation of the arm- 

 joint extending the full width of the scapulae, the latter distinc- 

 tion being very striking as well as the consequent greater strength 

 of the rays. The surface seems obscurely granulose, but is not 

 distinctly preserved. 



Rare in the carboniferous limestone of Hook Head, co. Wex- 

 ford. 



(Col. University of Cambridge.) 



[Inarticulata.) 

 Platycrinus vesiculosus (M'Coy). 



Sp. Char. Bodj/ spheroidal, depressed; visceral portion hemi- 

 spherical, deeper than the cup ; pelvis pentagonal, small, flat- 

 tened ; scapula small, rotundato-quadrate, one-third wider than 

 long, very thick, gibbous, slightly concave in the centre, lower 

 edge hanging below the pelvis, excavation for the first arm- 

 joints very small, round, marginal, less than one-third the 

 depth of the scapulae ; visceral plates very large, irregular, po- 

 lygonal, some of them nearly equalling the scapulae in size, 

 they are moderately convex, and each rendered rugged by se- 

 veral small tubercular projections ; mouth lateral, surrounded 

 by small plates. Length of small specimen from pelvis to 

 vertex 6 lines, width 8 lines. 

 The very large, bubble-like tuberculation of the visceral plates 



and the small, gibbous scapulae give a most peculiar aspect to this 



species, quite unlike any other I am acquainted with. I find 



the characters very constant. 



Not uncommon in the carboniferous limestone near Bake well, 



Derbyshire. 



{Col. University of Cambridge.) 



