BRIEF SYSTEMATIC SURVEY OF THE HEXACTINELLIDA 

 DESCRIBED IN THIS REPORT. 



Order HEXACTINELLIDA or TRIAXONIA. 



Sponges with very loose soft parts, and with siliceous spicules, which are either 

 isolated or united into a connected framework, and lielona; or are reducible to the triaxial 

 system. 



Suborder I. LYSSACINA, Zittel. 



Hexactinellida in which the spicules either remain altogether isolated, or are in part 

 subsequently and irregularly united by siliceous masses or transverse synapticula. 



Tribe I. HEXASTEEOPHOEA, F. E. S. 



Hexasters are always present in the parenchyma. The ciliated chambers are sharply 

 separated from one another, and are thimble-shaped. 



Family I. Euplectellid/E, Gray. 

 The dermal skeleton contains sword-shaped oxyhexacts with long proximal ra5^ 



Subfamily 1. Euplectellin.e, F. E. S. 



Tubular forms with transverse terminal sieve-plate. The lateral wall exhibits 

 circular parietal apertures. The projecting distal ray of the dagger-shaped hexact 

 dermalia bears a floricome. 



Genus 1. Euplectella, Owen. 

 With basal root-tuft. Parenchymal oxyhexasters. 



