Sponges from the Atlantic Ocean. 403 



Stellctta pachastrellouh'Sj n. sp. (LM. X\'. lig. 40, &c.) 



General form large, flat, thick, irregularly undulated, amor- 

 ])li()us, composed ot" a contused mass ot" spicules ; margin thick, 

 routui, and also irregularly unduluus, except \vhere it apj)earH 

 to liave been broken off from the submarmc object to which 

 tiie sponge had been attached. Colour cream-yellow. Upper 

 and under surfaces so much alike as to be almost undistinguish- 

 able, the former undulating, even, asj)erou3 from projection of 

 the ends of tiie large spicules, which are more or less con- 

 fuse<lly and horizontally imbedded in the dermal sarcode ; 

 the latter similar, but more granular, and sometimes indicated 

 by the impressions of small pebbles on which the sponge may 

 have rested while growing ; the whole more or less enveloping 

 small objects such as minute Foraminifera [Glohigerina)^ small 

 shells, itc, also overgrown by a variety of other sponges. 

 Pores chiefly in the dermal sarcode, tympanizing the interstices 

 between the projecting spicules. Vents single or in groups, 

 more or less irregularly scattered over both surfaces, especially 

 the lower one. Internal structure more compact, consisting 

 also of a confused mass of Sjiicules held together by cancellated 

 sarcode, traversed by the branched canals of the excretory 

 system, which chiefly run towards the lower surface, where 

 they end in the vents mentioned. Spicules of two kinds, viz. 

 skeleton- and flesh-spicules. Skeleton-spicules of three forms, 

 viz. : — 1, zone-spicule, comparatively small, consisting of a 

 three-armed shaft, arms equal, equidistant, simple, smooth, 

 sharp-pointed, expanded almost horizontally and slightly 

 recurved; shaft about twice the length of the arm, straight, 

 smooth, sharp-pointed, 60- by 5-1800ths inch, arm 35- by 

 4-1 sooths inch (PI. XV. fig. 40, h) ; 2, body-spicule, very 

 large simple acerate, slightly curved, and sharp-pointed, 260- 

 by 7-1800ths inch (fig. 40, «) ; 3, anchoring-spicule, a three- 

 armed shaft, arms equal, equidistant, simple, smooth, sharp- 

 pointed, at first expanded for a short distance, and then sud- 

 denly bent backward; shaft thin and very long, smooth, straight, 

 8hari)-pointed, 260- by l^-1800th inch long, anus 12- by H- 

 1800th long (fig. 40, c, //). The forked form not observed. 

 Flesh-spicules of four forms, viz. : — 1, long, simple, acerate, 

 slightly curved and thickly microspined, b^- by 14-6O00th 

 inch, but very variable in size (fig. 40, f/, j); 2, short, sinq)le, 

 acerate, cuned or bent in the centre, with or without central 

 inflation, pointed or obtuse at the extremities, thickly micro- 

 spined, 11- by 2-6000ths inch (fig. 40, f'); 3, globular stellate, 

 of 6 or 7 rays, rays micqual, microspined at the extremities. 



