Young Specimens q/Antlienea sp. 297 



interrarlial ]:)lnte to an interbiaclilal arc. Tlie plates are 

 almost Iriaiif^ular, witli the bases of opposed plates p:\ia! lei. 

 Proximally they are about 1 nun. in dianieter, hut the pair in 

 contact with the supero-inarorinals is less ; there i^ a faint 

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

 slig-htly laro-er distall}^ than proximally. All the plates of the 

 a))ical system excepting the interradials bear tuberoles, which 

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

 The central plate is composed of large o-nmules which are 

 lieaped close together. There are about thirty-four and 

 eiglity-four tubercles on the abactinal ))lates of the respective 

 specimens. 



On the actinal surface the ventro-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 anibulacral 

 groove, extending to the third or fourth infero-marginal j)late 

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

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

 cellarire. 0:i the whole, the actinal face presents a closely 

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

 side of and parallel to the anibulacral groove; it is closely 

 paved with very small round granules. Ikying in the furrow 

 are a number of small pedicellariffi with their long axes 

 parallel to the groove. At tbe 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 ])ersistence of what was once a second row of adambu- 

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

 uj)turned, the spines would serve tbe purpose of very effective 

 armature to an ex])osed part. 



The adambulacral plates have three or four short, blunt, 

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

 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 o'hcr throughout. 



There are fourteen supero-marginal and fourteen intero- 

 marginal ])lates; both are gianulate 1 and take part in forming 

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

 between the two sets of plates. Tiie supero-inarginals are 

 convex and very prominent ; at the interbrachial arc they 

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

 The granulations r(!semble a mosaic of small platens, are 

 distinct, of varying size, and generally round and slightly 

 convex. Arranged transversely on these |ilate.s are one to 

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



Ann. & Mar/. N. Hist. Scr. 0. Vol. vi. 20 



