SILICEOUS SPONGES. 211 



very distinct rows; the interspaces are rounded, and from 1 to 1'8 mm. in width. 

 The canal-apertures are in some cases partially bridged over by extensions of the 

 dermal layer. I have not been able to ascertain the characters of the interior or 

 cloacal surface. 



The dermal layer is composed of spicules having a stellate disposition of the rays 

 so as to leave minute circular or irregular interspaces. The interior mesh is regular ; 

 the spicules are about '04 mm. in thickness, and the distance between the nodes is 

 about '25 mm. The nodes are compact. 



The regular mode of growth and the arrangement of the canal-apertures readily 

 distinguish this from the only other branching species of this genus, S. ramosus, 

 Quenst. sp. 



The unique specimen is partially imbedded in a calcareous matrix ; it retains its 

 siliceous structure in beautiful preservation. 



Distribution. Neocomian : Santander, Spain. 



2e2 



