250 DE. HINBE AND ME. HOLMES OK SPOIS'GE-EE VFA USTS 



smooth and rounded, but not inflated. The axial canal in the 

 shaft of the spicule is much enlarged, and there is a rounded 

 inflation at the top from which extensions are given off into the 

 rays. Length of shaft (incomplete) •12 mm., thickness "008 mm. ; 

 length of rays "031 mm., thickness "0066 ram. Scopules somewhat 

 similar to this fossil, but with more slender rays, are present in 

 Hexaetmella ventilabrum. Carter (see Chall. Rep. vol. xxi. pi. xcvi. 

 figs. 7, 9). 



Detached Spicules of Hexactlnellicl Sponges. 



PI. XV. fig. 27. Sj)icule with five smooth rays, the proximal 

 ray straight and subcylindrieal, whilst the transverse rays are 

 slightly arched and tapering. The rays are traversed throughout 

 by axial canals. Length of proxinial ray "235 mm., of transverse 

 rays '215 mm. 



PI. XV, fig. 28. Spicule with four stout equal rays in a plane, 

 the rays curved slightly near the ends, which are obtuse and 

 thickly set with minute spines or tubercles, the rest of the spicule 

 smooth. Length of rays "19 ram., thickness "028 mm. Similar 

 four-raved spicules are present in recent species of Syalonema ; 

 according to Schulze they occur in the basal pad of the lower 

 portion of the body of the sponge. A similar form to this fossil, 

 but larger, occurs in Hyalonema tenerum, Sch. (Chfill. Rep. vol. 

 xxi. p. 224, pi. xxxi. fig. 15), from the South Pacific, at a depth 

 of 2550 fathoms. 



PL XV. fig. 29. Spicule with four unequal rays in a plane ; 

 the rays of one axis are elongate, tapering, and acutely 6nded, 

 whilst those of the other axis are shorter and somewhat obtusely 

 ended. Except in the centre, the rays are set with short conical 

 spines. The centre is slightly inflated. Length of the principal 

 rays -22 mm., of the shorter "153 mm., thickness of the rays at 

 the base "028 mm. 



PI. XV. fig. 30. Spicule with six subequal, slender, slightly 

 cur^^ed rays, which taper to an acute point and are covered with 

 small spines. Length of rays -095 mm., thickness -01 mm. 



Crater am orplia (c). — PI. XV. fig. 31. Spicules with six (?) rays 

 originally, two of them are now only represented by scars ; the 

 rays short, thick, and rounded at the ends. The axial canals are 

 very distinctly shown. This form resembles the spicules of the 

 stalk of Crateromorpha Meyeri, Gray (see Chall. Eep. vol. xxi. 

 pi. 61. figs. 5, 6), from near Zebu, but it is much larger. 



