CARNOSA. 95 



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



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

 Soil.; Gastrophanella 0. S. ; Setidium O. S. ; Poritclla 0. S. ; Amphibleptula 

 0. S. ; Trcmaulidium 0. S.; Lciodcrmatium 0. S.; Sympyla Soil. 



Fam. 2. Anomocladidae. Desnia 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 tetmxial 

 type present or absent. 



Tribe 1. MICROSCLEROPTERA. Microscleres are variously modified tetrac- 

 tinose asters, candelabras, or minute trifenes. 



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. PlaMna 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.; Rhacclla Soil. 



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

 amphiaster. Ectosome thin and not sharply marked oti' 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. Astropcplus Soil. 



Tribe 2. OLIGOSILICINA. With asters only. 



Fam. Chondrillidae. Chondrilla 0. S. 



Tribe 3. MYXOSPONGIDA. Without spicules. 



Fam. Gumminidae. Chondrosia 0. S. , diplodal rhagon chambers ; Oscarclla 

 Yos., chambers eurypylous and rhagose. 



Order 3. MONAXONIDA.| 



Silicious skeleton with uniaxial megascleres. 



The Mondxonida are related to the Tetractinellida through the 

 AstropeplidcB 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. 



