1886.] 



POSITION AND CLASSIFICATION OF SPONGES. 



563 



developed and branched or covered with disks or scales. The oppo- 

 site ray smooth or absent. The other four equal (tangential). 



7. Scopulce. 



Fork- or broom-shaped spicules consisting of a long shaft traversed 

 by an axial rod, to the distal end of which some, generally four, 

 slender anaxial rods are attached. 



8. Amphidisc. 



A rod with an umbrella-shaped disk at each end. 



9. TJncinatcE. 



A rod with recurved hooks throughout its entire length. 



10. Clavulce. 



A rod pointed at one end and bearing a knob or disk at the other. 



4. Tetraxonia. 

 With four axes radiating from one point. The ends of the 

 spicules lie in the corners of a square pyramid and their derivatives. 



A. Tetractina. 

 B. Triactina. 



C. Diactina. 



"With four rays. 



With three rays. 



With two rays. 



D. Monactina. 

 With one ray. 



For the reasons given above, I shall abstain from describing the 

 Tetraxonian spicules in detail. I will, however, mention the terms 

 for spicules employed by Sollas in his preliminary report (1453). 



These, alphabetically arranged, are the following : — 



Acerate (Monaxon). 



Acerella (Mouaxon ?). 



Ampliinster (?). 



Ampbiastrella (Spirastrella ?). 

 «Amphitetrad. 

 »Anchor8. 



Anthaster (?). 



Arculus(?). 

 ♦Bifurcated Forks. 



Caltbrops (?). 

 ♦Candelabra. 



Cbiaster (?). 



Cylindrical spicules (Monaxonia ?). 



Echinella (?). 



Ectaster (?). 



Erdaster (?). 

 ♦Forlis. 



ifForks with trifurcate arms. 

 *Fu8iform Acerates (Monaxonia). 



Globate (Scleraster). 



Globules (?). 



Hispidating Acerate (Monaxonia). 

 *Oue-pronged (unicellate) Forks. 

 *Porrectate Forks. 



Pycnaster (?). 

 ♦Radical Ancbors. 



Sigmella (?). 

 «Sonial Ancbor. 

 ♦Somatic Ancbor. 



Spinispirulae (Spirastrella). 



Spirulfe (Spirulse). 



Stellate (?). 

 ♦Tetrad. 

 ♦Triona. 



Tricbite Acerates (Monaxonia). 

 ♦Triebite Forks. 

 ♦Trifid Forks. 

 ♦Two-pronged (dicellate) Forks. 



The names marked * presumedly apply to Tetraxon spicules. The 

 others probably belong to different groups. 



37* 



