— 29 — 
tions, in other instances they are bow-shaped or curved in 
the form of the letter C. One of the largest specimens is 
3,8mm long by 0,13mm wide; an average specimen measures 
2,25 mm long by 0,o9gmm. wide. They are very abundant. | 
These spicules correspond pretty closely with those which 
Mr. Carter discovered on the outer surface of some Atlantic 
sponges, to which he has provisionally given the name of 
Ophiraphidites tortuosus, it being at present doubtful whether 
they may belong to a distinct sponge or whether they are the 
acerates of a species of Pachastrella. (An. Mag. N. H. Dec. 
1876 p. 458). Similar spicules are also present in the Haldon 
Green ‘Sandy (An.:MagiN. Hy Vol 7 pi 131.'Pl. Xifig-* 79);; 
in the Westphalian Chalk, (Ueb. Coelop. Taf. IV. fig. 24, 25) 
and in the Eocene sand at Brussels. (Rutot: op. cit. Pl. 3, 
figs; (5,20). 
Simple and Compound Trifid Spicules of Geodia and 
allied Genera. 
Geodia? clavata n. sp. 
(Plate I. fig. 4. plate II. figs 1—5.) 
Very robust spicules with an elongate, straight or slightly 
curved shaft, constricted immediately beneath the head; below 
this, there is a bulbous inflation from which the shaft gradually 
tapers to a point. The head rays in all the simple forms, and 
in some of the compound as well, are but little more than 
short rounded knobs (fig. 1 —35); in other compound heads 
the rays are more compressed and bifurcate into small pointed 
extensions. In some instances the number of the rays is 
limited to two. (fig. 1). The interior canal of the shaft is 
partially preserved; in some spicules it may be seen to extend 
throughout the entire length; in others only traces of it are 
exhibited in the inflated portion of the shaft, where it is 
expanded in the same manner as the shaft itself. Very 
rarely are canals exhibited in the head rays. In some spicules, 
which at first I thought might be acuate spicules with bul- 
