— 35 — 

 Geodia? sp. 



(Plate II, figs. 13, 14, 15). 



Spicules with an elongated, moderately robust, straight, 

 shaft, having a constriction at the upper end, below which, 

 in some specimens, there is a slight inflation; the shaft 

 gradually tapers to a point. The rays of the head are short, 

 slightly curved at their junction with the shaft, then straight 

 and pointed. They extend forwards nearly in a line with the 

 shaft itself. Specimens with the rays bifurcate or compound 

 are equally as numerous as those with the rays simple. These 

 spicules are well characterized by the constriction at the top 

 of the shaft and by the manner in which the head-rays ex- 

 tend directly forwards. The length of an average specimen 

 is 2,29 mm.; thickness of shaft 0,135 mm.; and width across 

 the head 0,2 mm. A spicule with a similar diposition of the 

 head rays but apparently a larger form, is figured from the 

 North of Ireland (Wright: op. cit. PI. II, fig. 22). 



This and a few other forms of spicule, described below, 

 in which the head rays are either directed forwards or else 

 recurved, appear to resemble those spicules of Mr. Carter's 

 group of the Pachytragidae which he has termed « anchoring » 

 spicules and it is probable that they were associated with 

 the larger trifid spicules, which I regard as the «zone» spi- 

 cules of the same division of sponges. As a rule these fossil 

 «fork» and « anchor* spicules are much larger than those in 

 existing sponges, biit this might be expected from the greater 

 dimensions of the «zone» spicules. 



Geodia, sp. 



(Plate II, figs. 17, iS, 19). 



Somewhat delicate spicules with an elongate gradually 

 tapering shaft, and simple, straight or curved, pointed rays 

 extending forwards from the shaft. The rays are frequently 



-5 Jlr 



