73 



all these spicules appear to have been smooth but there occur 

 fragmentary spicules (Plate V, fig. 27) consisting of a straight 

 nearly cylindrical shaft from the surface of which numerous 

 minute recurved spines project, which probably are the shatts 

 of anchoring spicules. Both the anchoring spicules and the 

 spinous shafts are very rare. 



The resemblance of these anchoring spicules to those of 

 existing sponges of the sub-order Lyssakina is sufficient to 

 prove that they belonged to this group, and not improbably 

 to the same sponges as the free hexactinellid spicules already 

 described. A comparison may be made with the figures of 

 several kinds of anchoring spicules of existing sponges given 

 by Mr. Carter (An. Mag. Nat. Hist. S. 4, Vol. 12, PL XIV) 

 also with those of Rossella antarctica , Carter (An. Mag. 

 Nat. Hist. S. 4. Vol. 9, PL XXI). Similar shaped but larger 

 anchoring spicules also occur in Hyalostelia (Hyaloneina) 

 SmitJiii Young and Young (An. Mag. Nat. Hist. S. 4, Vol. XX, 

 PL XIV) and more recently Mr. Carter has found them fossil 

 in carboniferous strata near Sligo in Ireland (An. Mag. Nat. 

 Hist. S. 5, Vol. 6, p. 211, PL XIV, fig. 9). Mr. Wright has 

 also figured a small four armed anchoring spicule with spi- 

 nous shaft from the Irish Chalk (op. cit. PL II, fig. 23 a, b). 



Spicules with Borings. 



(Plate V , figs. 28, 29). 



Out of several hundreds of sponge spicules from Hor- 

 stead which I have examined under the microscope, there are 

 a few which give distinct evidence of having been perforated 

 by some organism. The perforations are of the form of 

 simple, unbranched, elongated, cylindrical tubes extending for 

 various lengths in the interior of the shafts of acerate and 

 trifid spicules. The tubes are sometimes curved and smooth, 

 but occasionally they are convoluted and twisted. They ter- 

 minate blindly in the interior of the spicule. In some 



