212 



ME. W. PEECT SLADEN ON THE 



directed adorally. In tlie outermost row, however, on each side of 

 a ray, this arrangement is more or less modified in consequence 

 of lateral compression of the paxillse-crowns — these being more 

 compact and with the spinelets less regular in their disposition. 

 The oscular orifice is large and very conspicuous, the valves 

 composed of ahout a dozen moderately long, rather fine spinelets, 

 all of which are webbed together ; the valves expanding fan-like 

 when opened, and forming a prominent vertical wall to the ori- 

 fice. The spiracula are small, very numerous, closely and equi- 

 distantly placed, occupying the whole interspace between adjacent 

 paxillar crowns. Very remarkable elongated tracts or lines of 

 spiracula and an accompanying wrinkled membrane extend from 

 the paxiUiferous radial areas out upon the fleshy interbrachial 

 membrane, which has the appearance of being inlaid with them. 

 These lines are slightly curved, nearly equal in length to the half 

 of the radial area, placed regularly parallel with one another and 

 directed at an angle inward in relation to the direction of the ray. 



Ambulacra] furrows broad, almost straight, very slightly peta- 

 loid. Ambulacral suckers large and robust, arranged in simple 

 pairs. Ambulacral spinelets, one to each plate, rather short, 

 invested with a wide membrane which extends beyond the tip as a 

 saccular prolongation twice as long as the spinelet itself. Aper- 

 ture-papillse large, fleshy, subspatulate or oval, occupying nearly 

 the whole space between the bases of the actino-lateral spines. 



Mouth-plates forming a broad rounded ridge at their line of 

 junction, prominent aborally. Each plate bears one sliort secon- 

 dary surface-spine with wide investing sacculus, placed about 

 midway on the plate, quite behind the mouth-spines, the pair 

 being very widely separated. Mouth-spines 3, short, conical, 

 placed on the margin of the lateral flange of the plate, with sac- 

 cular investments. 



Actino-lateral spines about 45 -|- in number on each side of a 

 furrow, hidden in the thick fleshy tissue, which forms little chan- 

 nels or wrinkles between each, giving a fluted appearance to the 

 interbrachial area on tlie underside of the Starfish. The longest 

 spines are little more than the extreme breadth of the ambulacral 

 furrow — a wide space, greater at the margin than the length of the 

 spines themselves, intervening in the interbrachial area between 

 their extremities and those of the spines of the neighbouring ray 

 The spines are directed slightly backward {i. e. adorally in relation 

 to the direction of the ray) ; and the series of those spines whose 



