DEMOSPONGLE. 93 



Sub-order 2. DICTYONINA. 



Hexactinellida in which the large parenchymal hexacts are from the first more 

 or less regularly united as dictyonalia in a firmly -connected framework. 

 Tribe 1. UNCINATAKIA. With uncinates. 



A. With clavulce. 



Fam. 1. Farreidae. Farrea Bow. 



B. With radially disposed scopulce. 



Fam. 2. Euretidae. Eurete Carter; Periphragella Marshall; Lefroyella 

 Wy. Th. 



Fam. 3. Melittionidae. Aphrocallistes Gray. 



Fam. 4. Coscinoporidae. Chonelasma F. E. S. 



Fam. 5. Tetrodictyidae. Hexactinella Carter ; Cyrtaulon F. E. S. ; Fieldingia 

 S. Kent; Scleroihamnus'W. Marshall. 



Tribe 2. INERMIA. Without uncinates or scopulfe. 



Fam. 1. Maeandrospongidae. Dactylocalyx Stutchbury; Margaritella 0. S. ; 

 Scleroplegma 0. S. ; Myliusia Gray ; Aulocystis F. E. S. 



Order 2. HEXACERATINA. 



Sponges with large and saccular ciliated chambers, with simple 

 canals. Skeleton composed of soft horny fibres, sometimes accom- 

 panied by horny spicules. The skeleton may be absent. 



Fam. 1. Darwinellidae. Skeleton comprises both horny fibres and horny 

 spicules. Darwinella Fr. Mliller. 



Fam. 2. Aplysillidae. Skeleton is composed of horny fibres only. lanthella 

 Gray; AplysillaF. E. S. ; Dendrilla Lendf. 



Fam. 3. Halisarcidae. Skeletal structures absent ; chambers syconate. 

 Halisarca Duj. ; Bajulus Lend. 



Class III. DEMOSPONGIJE. 



Without triaxonic spicules, with small choanocytes and small ciliated 

 chambers. Skeleton of silicious spicules, or of spongin, or of both 

 combined. 



Order 1. TETRACTINELLIDA.* 



Skeleton characterised by tricene or tetraxon megascleres, or lithistid 

 desmas. 



The genus Placospongia, which is without the skeletal characters, 

 is included here because of the presence of sterrasters which are not 

 found outside the group. 



Sub-order 1. CHORISTIDA. 



Tetractinellida in which lithistid desmas are absent, and the megascleres are 

 never articulated to form a coherent skeleton. 



Tribe 1. SIG-MATOPHORA. Microsclere when present a sigmaspire. 



* W. J. Sollas, " Report ,on the Tetractinellida." Challenger Reports, vol. 

 25, 1888. E. Topsent, "Etude Monographique des Spongiaires de France. 

 I. Tetractinellida." Arch. d. Zool. exper. et gen.^(3) T. 2, 1894. 



