KEPOET ON THE ASTEEOIDEA. 297 



1. Nijmphaster symbolicus, n. sp. (PI. L. figs. I and 2 ; PI. LIII. figs. 7 and 8). 



Rays five. R=85 mm. ; r=26 mm. R>3"25 r. The minor radius is thus in the 

 proportion of about 30 per cent. 



General form flat and thin. Disk large and pentagonal. Rays elongate, narrow, and 

 tapering continuously to a slender extremity ; width midway between the centre of the 

 disk and the extremity, 8 '25 mm. ; width at the commencement of the outer fourth, 

 4 mm. Interbrachial arcs wide and openly rounded. 



The marginal plates are broad and massive, the outer part forming a vertical lateral 

 wall, the abactinal and lateral areas of the plate being at right angles to one another, with 

 the junction abrupt and subangular. The intermediate paxillar area is on a level with the 

 supero-marginal plates, and the section of the ray is almost rectangular in outline, its 

 horizontal diameter being twice the vertical near the base of the ray, but decreasing in 

 proportion as it proceeds outward. The supero-marginal plates are thirty-three in number 

 from the median interradial line to the extremity. Their length is little more than their 

 height, and their breadth is nearly twice their height. On the outer part of the ray the 

 length is greater than the breadth, the height remaining the least dimension. The surface 

 of the plates is covered with a uniform, small, semiglobular, miliary granulation. The 

 granules do not touch one another, but closely cover the whole plate, and at the lateral 

 margins form a lineal series which helps to define the sutures between adjacent plates. The 

 median surface of the plate is faintly convex. Each of the plates, except at the end of the ray, 

 may bear one or two long entrenched pedicellariae on the abactinal surface, and frequently 

 (at least in large specimens) a rather smaller one also at the angular junction of the abactinal 

 and lateral surfaces, but which may not, however, proceed very far along the ray. These 

 pedicellariae have the appearance superficially of a straight cut or slit about T25 mm. in 

 length, intersected midway by a very small but wider cross cut ; the jaws of the pedi- 

 cellariae have somewhat the form of the letter T, with its vertical line greatly prolonged ; 

 and when retracted, fit exactly in the excavations above described. The pedicellariae 

 have no definite posture on the plates. The odd terminal plate is comparatively large in 

 relation to the neighbouring marginal plates ; it is elongately shield-shaped, with the 

 angular extremity directed inward, and the outer portion of the plate rounded sub- 

 cylindrically and contracting slightly and gradually towards the extremity, which is 

 obtuse. The infero-marginal plates correspond to the superior series, the rounding 

 towards the actinal area being rather more decided. They are covered with a precisely 

 similar small granulation, and each usually bears one of the entrenched pedicellariae on 

 the actinal surface. The breadth of the infero-marginal plates diminishes rapidly after 

 passing the base of the ray, and thence to the extremity the length becomes the largest 

 dimension. 



The armature of the adambulacral plates consists of a furrow series of ten delicate, 

 rather elongate spinelets, flattened laterally to a uniform thickness but tapering towards 



(ZOOL. CHALL. EXP. — PART LL — 1S8S.) 38 



