JAPANESE ASTEEOIDEA. 113 



" Hyplialaster inermis, n. sj). 



" Marginal contonr stellato-pentagonoid. Kays five, ■\^-ell developed, 

 slender, round, and tapering but slightly. Interbrachial angles very wide 

 and expansive, the curve shghtly flattened in the immediate angle, thereby 

 emphasizing the marked pentagonal contour of the body-disk. The lesser 

 radius is in the proportion of 42.5 per cent.; R=:20 miUim., r=8.5 miUim. 

 Disk depressed, not inflated ; both dorsal and actinal surfaces stand on a 

 level with the edges of the marginal plates. 



" Dorsal area covered with closely crowded paxillse, the whole disk as 

 well as the base of the rays being uniformly packed. The paxillee are veiy 

 fine and small, and are made up of about 5 to 10 spinelets ; towards the 

 margin of the disk they become smaller and also in the centre, where they 

 are very compact, a shghtly prominent peak being formed as in Gtenodiscus. 

 A slight elevation of the sui'face is present in the median radial Hne, oppo- 

 site the base of each ray, and at about one third of the distance from the 

 margin to the centre. 



" Marginal plates occupy the entire margin and represent the whole 

 thickness of the animal, forming perpendicular walls regularly rounded above 

 and below. Along the rays the supero-morginal plates meet in the median 

 dorsal line and form a complete casing to the ray, which is w^ell rounded, 

 small, and tapers but shghtly. The supero-marginal series are 8 in number 

 (or, with a veiy small aborted one, 9), exclusive of the terminal. The j)lates 

 which faU in the margin of the disk proper have the length about equal to 

 their height, but in those along the ray the height is greater than the length. 

 The infero-marginal plates correspond in number and in length with the 

 superior series. In the arm-angle, along the disk proper, the height is about 

 equal to the length and the plates are miiform in size with the superior 

 series ; towards the extremity of the ray the height diminishes gradually and 

 the length is greater than the height — a reversal of the relative proportions 

 presented by the plates of the superior series. The marginal plates are 

 smooth and bear no spines, but when examined microscopically have the 

 appearance of being subgi'anular and built up of a rather open network. 

 The plates of both series are convex outwardly or tiunid in a veiy sHglit 



