/ 



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CO s, GOTO : 



fiud form ji largo arcliecl or tubercular plato, iudouted ou its outer margin, 

 aud bearing tlu'oe more or less prominent tubercles— the »udiments of dorso- 

 margiual spines. Tlie fuiTOAvs between the marginal plates are continued 

 onto the actinal sm-face of the animal and extend to the ambulacral fmTOw, 

 cutting up the ventral inten-adial areas into band-like spaces, each of wliich 

 is tessellated ^ith irregular, subquadrate, scale-like plates that imbricate upon 

 one another, and form normallj-, in large adult examples, a douille alternating 

 series boliind each adambulacral plate. The innermost baud, however, of 

 each area comprises two adambulacral plates ; aud the trapezoid tessellating 

 scales, wliich here always form a regular double alternating series, are, in 

 consequence, twice as largo in the neighbourhood of the fm-row as the scales 

 in the other bauds. All these plates bear on the margin that opens on the 

 sutm-al fm-row a series of papillae that form a continuation with the X)apilla9 

 above-noted on the sides of the lateral jjlates, from wliich they differ only in 

 being not flatteuedi nor are they at the same time so regular aud closely 

 placed. The adambulacral x)late represents a wedge-shaped x^i'ojection into 

 the fm-row, and carries five or six papillaî, three only of wliich usually stand 

 on the margin of the ambulacral furrow, the remaining two or three (which 

 are generally much smaller) being situated on the aboral margin opening on 

 the sutm-al f iutow of the interbracliial area ; not uufrequently, however, one 

 of them is as large as the ambulacral spinelets, and is placed somewhat 

 inward upon the plate, away from the sutm-al fringe aud behind the am- 

 bulacral series. Towards the extremity of the ray the adambulacral plates 

 stand next to the veutro-margiual x^lates, and are not separated from them 

 by the trapezoid imbricating scales above described. 



"[Each pair of mouth-plates forms an ovoid mass, the inner or apposed 

 margins of the plates being elevated into a prominent keel. The inner- 

 most pair of mouth-papillsG are very large and thick, and taper to a point — 

 the remainder, from 7 to 9 in number, being considerably smaller and 

 an-anged round the free margin of the plate. Along, or near to, the median 

 keel of the mouth-plate are 3-5 coarse spinelets, the innermost being large 

 and thick, and are much loss pointed than the marginal series. The mad- 

 reporiform body is frequently not more than its owu diameter distant from 



