37 



meter of the shaft 0,18 mm.; and the width across the head 

 rays 1,37 mm. The length and spreading disposition of the 

 rays give these spicules an altogether different appearance to 

 those which I have already referred to Geodia. They are not 

 uncommon in the flint-meal. 



The only fossil spicules, which, to my knowledge, at all 

 resemble these specimens, are those of Tethyopsis Steinmanni, 

 Zittel (Stud, iiber foss. Spong. p. 99, Taf. XI, fig, 3) from the 

 Upper Chalk at Ahlten in Hanover. 



Tethya? sp. 



(Plate III, fig. 10). 



Simple trifid spicules with elongated gradually tapering 

 shaft and three equal, short, conical, slightly curved and pointed 

 rays, projecting forwards at a wide angle with the shaft. Average 

 length of large spicule 2,47 mm.; diameter of shaft 0,135 mm.; 

 width across the head rays 0,83 mm. Not uncommon. 



Tethya? sp. 



(Plate III, fig. 4). 



Simple trifid spicule, shaft straight, stout, rapidly taper- 

 ing; head rays short, cylindrical and nearly at right angles 

 to the shaft. Length of spicule 2,29 mm.; diameter of shaft, 

 0,315 mm. extension of head rays 0,8 mm. This peculiar 

 shaped, robust spicule occurs but rarely. It has been found 

 in the Chalk of the North of Ireland (Wright: op. cit. p. 89 

 PL II, fig. 12) and Dr. Bowerbank states that a similar form 

 is present abnormally in some species of Tethya, but at pre- 

 sent I have failed to find any representation of a similar 

 spicule. 



Tethya? sp. 



(Plate III, fig. 5).' 



Robust simple trifid spicule with stout, straight, tapering 

 shaft and conical, straight, moderately long, obtusely pointed 



