CALCAREA. 19 



Spicules (Figs. 55 and 56). 

 The Oxea are of one sort : — 



(a) Very large bent projecting oxea, of all sizes from 400 m to 1,830 m long, x 

 20 m to 33 m thick, pointed at both ends, usually straight for about two- 

 thirds of their length, then bent at two or three points angularly, the end 

 being often bent through a total angle of 125° from the axis of the 

 straighter portion of the spicule. The points where the angular bends 

 occur are often marked on the, convex side by flattened areas, as if the 

 spicule had been deflected by contact with a plane surface. 



The Triradiates are of one sort : — 



{h) Alate triradiates of very variable shape. There is no distinction between 

 the gastral, body wall and dermal triradiates. Basal ray straight, tapering, 

 sharply pointed, 190 m to 366 m long x 10 m to 14 m thick. Paired rays 

 straight or bent slightly up or down, 160m to 220m long x 10m to 14m 

 thick. Tapering slightly and rather bluntly pointed. Oral angle 110° to 

 145°. 



Quadriradiates. — There is one sort of quadriradiate : — 

 (e) Alate quadriradiates from the gastral cortex, basal ray straight, tapering to 

 a sharp point, 280 m long x 12m thick. Paired rays equal, slightly bent 

 upwards, 140 to 220m long x 10 to 12m thick. Oral angle about 130° 

 folded backwards, i.e. away from the face bearing the apical ray. Angle of 

 fold about 170°. Apical ray 40 m long x 8 to 10 m thick, sharply pointed, 

 bent orally. 



Oscular spicules. 



(/) The oscular fringe cansists of short club-shaped oxea tapering to a point at 

 the inner end and bent near the outer end, which is rounded, 150 m to 

 230 m long X 12 m to 45 m thick. The thicker spicules are the commonest. 

 The triradiates at the edge have an oral angle of nearly 180°. 



Leucandra hiberna.* 

 (Plate XXXI., Figs. 57-58.) 



There are two specimens of this new species in the collection, one straight, vase- 

 shaped, 7 mm. X 1| mm., the other bent through at right angle, 6 mm. X 1 mm. In 

 colour they are dull yellow as preserved' in spirits, and appear minutely hispid to the 

 naked eye. 



The structure of the body wall, which surrounds a large gastral cavity, is shown in 



* Most of the specimens were collected at the ' Discovery's ' Winter Quarters. 



