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 7ethyopszs Steinmannz, 
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 egua/, 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. Il, 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 WF tics 15): 
Robust simple trifid spicule with stout, straight, tapering 
shaft and conical, straight, moderately long, obtusely pointed 
