54 



and I have myself obtained them in great abundance in ma- 

 terial from Coesfeld. 



Lyidium cretacea, n. sp. 



(Plate IV, figs. 1013). 



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 L. Zitteli^ 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. 1423). 



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 



