DEMOSPONGLE. 93 



Sub-order 2. DICTYONINA. 



Hexactincllida in which the. large parenchymal hcxacts are from the first more 

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

 Tribe 1. TJNCINATARIA. With unciuates. 



A. With clavulce. 



Fain. 1. Farreidae. Farrca Bow. 



B. With radially disposed scojmlce. 



Fani. 2. Euretidae. Eu,retc Carter ; Periphragella Marshall ; Lcfroyella 

 Wy. Th. 



Fani. 3. Melittionidae. Aphrocallistes Gray. 



Fani. 4. Coscinoporidae. Chonelasma F. E. S. 



Fani. 5. Tetrodictyidae. Hexactinella Carter; Cyrtaulon F. E. S. ; Ficldingia 

 S. Kent; Sclcrothamnus W. Marshall. 



Tribe 2. INERMIA. Without uncinates or scopulns. 



Fani. 1. Mseandrospongidae. Dactyl ocalyx Stutchbury; Margaritella 0. S. ; 

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



Order 2. HEXACERATINA. 



Sponyes n-ith larije and saccular ciliated chambers, with simple 

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

 panied by horny spicules. The skeleton may be absent. 



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

 spicules. Danrinella Fr. Miiller. 



Fani. 2. Aplysillidse. Skeleton is composed of horny fibres only. lanthella 

 Gray ; Aplysilla F. E. S. ; Dcndrilla Lendf. 



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

 Hulisarca Duj.; Bajulus Lend. 



Class III. DEMOSPONGI^. 



Without triaxonic spicules, irifJi small choanocytes and small ciliated 

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

 combined. 



Order 1. TETRACTINELLIDA.* 



Skeleton characterised by tri/ime or tetraxon megascleres, or lithistid 

 desmas. 



The genus Placospomjia, 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. SIGMATOPHORA. 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. 



