— 21 — 



pitted surfaces. Canals obliterated. In one instance (fig. ii) 

 there is a sharp bend in the upper portion of the spicule 

 whilst the lower part is straight and pointed. The largest of 

 these spicules is 2,9 mm. long by 0,13 mm. wide; the smaller 

 form (fig. 12) is 0,94 mm. long by 0,067 "irn. wide. In fig. 

 13, the head is much larger in proportion to the length; this 

 spicule is 0,832 mm. long by 0,15 mm. wide. All the 

 forms are rare. 



Acuate spicules similar in form but usually so much 

 smaller as to preclude a fair comparison are frequent in recent 

 sponges from the Atlantic and have been placed by Air. Carter 

 under the genus Halichondria (Ann. and Mag. Nat. Hist. S. 4, 

 Vol. XIV 1874, p. 16. PI. XV, fig. 40 b, 41 b. — Vol. 18, 

 PI. XV. fig. 29). Oscar Schmidt also figures a similar form 

 in Plocauiia gymnagusa (Atlant. Spong. p. 62, Taf. 4, fig. 17b) 

 and SoUas has also described hke spicules in other species 

 of the same genus (Ann. and Mag. Nat. Hist. July 1879 

 p. 44, PI. VI, fig. 3). Acuate spicules but with more deve- 

 loped heads appear in the Haldon Green Sand (Ann. and 

 Mag. S. 4, Vol. VII, PL X, fig. ■]■]) and also from the upper 

 Chalk at Coesfeld (Ueber Coelop. p. 37, Taf. V, fig. i — 10). 



There are two other forms of acuate spicules, in which 

 the thickest portion of the spicule is just below the head and 

 the spicule itself is straight and pointed (Plate I, figs. 14, 15). 

 The larger is 1,23 mm. long by 0,112 mm. wide, and 

 resembles in form a spicule from Haldon (Ann. Vol. 7, PI. X, 

 fig. 78) and the smaller is 0,517 m.m. long by 0,56 mm. 

 wide. 



Reniera, sp. 



(Plate I, figs. 18, 19, 22). 



Spicules of a regular conical form, the thicker end evenly 

 rounded and from this tapering either to a point or more fre- 

 quently ending obtusely. In rare instances, the smaller end 

 expands slightly, and the spicule becomes intermediate between 



