CARNOSA. 95 



Tribe 2. ANOPLIA. Special ectosomal spicules and microscleres absent. 



Fam. 1. Azoricidae. Desmas monocrepid. Azorica Carter ; Tretolophus 

 Soil.; Gastrophanella 0. S.; Setidium 0. S. ; Poritella 0. S. ; Amphibleptula 

 0. S. ; Tremaulidium 0. S. ; Leiodcrmatium 0. S.; Sympyla Soil. 



Fam. 2. Anomocladidae. Desma acrepid, consisting of a variable number of 

 smooth cylindrical cladi radiating from a thickened centrum. Zygosis between 

 the expanded ends of the cladi of one desma and the centrum of another. 

 Vetulina 0. S. 



Order 2. CARNOSA.* 



Sponges without megascleres ; microscleres belonging to the tetr axial 

 type present or absent. 



Tribe 1. MICROSCLEROPTERA. Microscleres are variously modified tetrac- 

 tinose asters, candelabras, or minute triaenes. 



Fam. 1. Plakinidae. With tetractinose, triactinose, diactinose asters, and 

 sometimes mono-, di-, or trilophous candelabra. Chamber-system eurypylous 

 or aphodal ; mesoderm chiefly collenchymatous. The sponge is divided into a 

 hypomere and a spongomere. PlaJcina F. E. S. ; Placortis F. E. S. 



Fam. 2. Corticidae. Tetractinose asters and candelabras. Aphodal or dip- 

 lodal. In part sarcenchymatous, in part collenchymatous. Corticium 0. Schm. ; 

 Calcabrina Soil. ; Corticella Soil. ; Rhacella Soil. 



Fam. 3. Thrombidae. Trichotriaenes, and sometimes a peculiar form of 

 amphiaster. Ectosome thin and not sharply marked off from choanosome. 

 Diplodal. Mesoderm densely collenchymatous with numerous large granular 

 cells in addition to collencytes. Thrombus Soil. 



Fam. 4. Astropeplidae. With microxeas and asters ; the microxeas are 

 arranged tangentially to the walls of the canal -system, forming a loose felt ; 

 eurypylous ; ectosome not a cortex. Astropeplus Soil. 



Tribe 2. OLIGOSILICINA. With asters only. 



Fam. Chondrillidae. Chondrilla 0. S. 



Tribe 3. MYXOSPONGIDA. Without spicules. 



Fam. Grumminidae. Chondrosia 0. S. , diplodal rhagon chambers ; Oscarella 

 Vos. , chambers eurypylous and rhagose. 



Order 3. MONAXONIDA.! 



Silicious skeleton with uniaxial megascleres. 



The Monaxonida are related to the Tetractinellida through the 

 Astropeplidce on the one]hand, and Plaldna on the other. In fact it 

 is difficult to see why these forms are placed in separate orders. 



Sub-order 1. HALICHONDRINA. 



Typically non-corticate ; skeleton usually reticulate ; megascleres usually either 

 oxea or styli. 



Fam. 1. Homorraphidae. Megascleres all diactinal, either oxea or strongyla ; 

 no microsclera. 



* E. Topsent, Arch. Zool. cxper. (3), 3, 1895. 



+ Ridley and Dendy, "Report on the Monaxonida." Challenger Reports, 

 vol. 20, 1887. E. Topsent, " Expose des Principes actuels de la Classification des 

 Spongiaires. " Revue Biologique du Nord de la France, t. 4. Id., "La classifi- 

 cation des Halichondrina." Mem. Soc. Zool. France, 1894. 



