and I have myself obtained them in great abundance in ma- 
terial from Coesfeld. 
Lyidium cretacea, n. sp. 
(Plate IV, figs. 10—13). 
Moderately robust spicules of very various forms, the 
branches sometimes expanded at their extremities but frequently 
elongated and obtusely pointed. The mesh work of the ske- 
leton of a more open character than in the preceding species. 
Average thickness of the spicules 0,09 mm. 
The spicules of this species can be readily distinguished 
from those of ZL. Zzttelz, by their lesser thickness, the greater 
frequency in which the spicular arms terminate obtusely and 
by the openings of the net work being proportionately larger 
Not very abundant. 
Genus Carterella, Zittel 1878. 
Carterella, sp. 
(Plate IV, figs. 14—23). 
Robust, straight or curved, elongated spicules, smooth, 
cylindrical or compressed, having at their extremities a small, 
thin, tongue-like prolongation frequently bent into a hook- 
like form. Occasionally the end of the spicule is blunted 
and forms a slight knob. The spicule is also, near the extre- 
mities, and sometimes in the centre, transversely grooved or 
deeply notched. As a rule, however the central portion of 
the spicule is smooth and rounded. Average length of spi- 
cule 1,5 mm.; average thickness 0,085 mm. Not infrequent. 
The sponges of this genus are long cylindrical bodies, 
composed of spicules, resembling those figured. These spicu- 
les are intertwined round each other, principally at their 
notched extremities, like the strands of a rope; the notches 
in the spicules permitting a very close union of the ends of 
the spicules with each other, while the central portions of 
