Young Specimens of Anthenea sp. 297 



interradial plate to an interbrachial arc. Tiie plates are 

 almost triangular, with the bases of opposed plates parallel. 

 Proxirnally they are about 1 mm. in diameter, but the pair in 

 contact with the supero-marginals is less ; there is a faint 

 fissure between the two rows. The pore-areas are round, 

 slightly larger distally than proxirnally. All the plates of the 

 apical system excepting the interradials bear tubercles, which 

 here number from one to three and measure less than 1 mm. 

 The central plate is composed of large granules which are 

 heaped close together. There are about thirty-four and 

 eighty-four tubercles on the abactinal plates of the respective 

 specimens. 



On the actinal surface the tentro-lateral plates are granu- 

 lated, slightly convex, ovoid in shape, and decreasing in size 

 as they approach the margin. There is a distinct row running 

 on each side of the furrow and parallel to the ambulacral 

 groove, extending to the third or fourth infero-marginal plate 

 (counting from the distal end). The inter-oral plate is pear- 

 shaped, and is the largest; several of the plates bear pedi- 

 cellarise. On the whole, the actinal face presents a closely 

 tessellated surface. There is a well-defined furrow on each 

 side of and parallel to the ambulacral groove ; it is closelv 

 paved with very small round granules, hying in the furrow 

 are a number of small pedicellarise with their long axes 

 parallel to the groove. At the distal end of the arm, and on 

 each side of the last two paired infero-marginal plates, are a 

 series of six small blunt spines, which may be the result of 

 the persistence of what was once a second row of adambu- 

 lacral plates. The actinal distal end of the arm being slightly 

 upturned, the spines would serve the purpose of very effective 

 armature to an exposed part. 



The adambulacral plates have three or four short, blunt, 

 oval spines, not always equal ; they are largest at the middle, 

 but toward the oral region become short and thick; here, too, 

 granules encroach upon their sides. There is one series only, 

 and the plates in it are in contact with each other throughout. 

 There are fourteen supero-marginal and fourteen infero- 

 marginal plates ; both are granulated and take part in forming 

 the sides of the arms ; a well-defined line runs round the arms 

 between the two sets of plates. The supero-marginals are 

 convex and very prominent ; at the interbrachial arc they 

 rise 1 mm. above the disc, but distally they are almost level. 

 The granulations resemble a mosaic of small plates, are 

 distinct, of varying size, and generally round and slightly 

 convex. Arranged transversely on these plates are one to 

 six irregular dome-like tubercles, the majority of the plates 

 Ann. & Mag. N. Hist. Ser. 9. Vol. vi. 20 



