246 Mr. F. M'Coy 07i some new Palaeozoic Echinodermata. 



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

 width 6 hnes, 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 differs 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 gi'eater 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. Body spheroidal, depressed; visceral portion hemi- 

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

 tened ; scapulae 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 ualike any other I am acquainted with. I find 

 the characters very constant. 



Not uncommon in the carboniferous limestone near Bakewell, 

 Derbyshire. 



{Col. University of Cambridge.) 



Platycrinus diadema (M'Coy). ■ 



Bp. Char. Body very much depressed, spheroidal (from the base 

 of pelvis to the vertex one- third less than the diameter between 

 the arms) ; pelvis large, depressed, pentagonal, without divi- 

 sional lines ; columnar adherence circular, crenated, one-third 

 the diameter of the pelvis, but seated in the bottom of a deep 

 circular excavation three-fourths the diameter of the pelvis ; 

 scapulae hexagonal, nearly twice as wide above as below, about 

 one-third wider than long, very slightly convex except at the 



