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generally one or two small tliornlets near tlie base of tlie spine, otherwise 

 the sui'face of the plate is simply covered with a very thin membranous 

 tissue. In the median inteiTadial line is a high, odd, supero-marginal plate, 

 thick and tubercular abactinally, which bears an elongate, cylindrical, taper- 

 ing spine, about 8 mm. in length, directed vertical] 3'. On the vertical wall 

 of the plate wliich stands in the interbrachial arc are a number of minute, 

 conical, sharply-pointed granules, usually along the median area ; and the 

 one or two neighbouring plates on each side are likewise similarly, but 

 irregularly and more sparsel}', granulated. 



" The infero-marginal plates are elongate and low like tlu^ supero- 

 marginal series, to which they coiTespond. Each plate bears a straight, 

 tapering, lateral spine articulated on a tubercle, and usually more delicate 

 and often shorter than the spine on the accompanying supero-marginal 

 pLate. A second but much smaller spine is sometimes present on the inner 

 side, usually in the large examples, but it is often wanting altogether, and 

 seldom appears on the inner part of the ray and towards the extremity. 

 Occasionally' one or two microscopic miliary tliornlets are present on the 

 plate, and the sm-face of the plate is covered with a delicate membranous 

 tissue. 



"In the median inteiTadial line there is a large, broad, odd infero- 

 marginal plate, larger and l)roader than any of the others ; it is placed 

 immediately beneath the odd supero-marginal plate. It bears a small 

 representative of the lateral spine, and in addition several delicate miliary 

 spinelets and tliornlets. The one or two next plates on each side are 

 likewise frequently' more sx^inukite than any of the others. 



" The adambulacral plates are large in proportion to the size of the 

 stai-fish, their length slightly exceeds their breadth, and they present a 

 prominent and rather al)rux)t convexity into the fiuTOW. Their arrnatm'e 

 consists of :— ( 1.) a fuiTOAv series of five to seven small, short, c}-lindrical, 

 obtusely tipped spinelets, suliequal excepting the exti-emities of the series, 

 wliich are rather shorter ; all are closely j^laced and form compact isolated 

 little combs. (2.) On the actinal siu'face of the plate is one comparatively 

 large; spinelet, robust at the base, and tapering to a pointed extremity ; on 



