SYSTEMATIC INDEX. 



2. Classis SILICEA 19 



1. Ordo HEXACTINELLIDA 19 



Subordo LYSSACINA 19 



Familia Efplectellid^ 19 



Genus Euplectella 19 



Familia Hossellidjs 20 



Genus Holtenia 20 



Familia Hyalonematid^ 21 



Genus Hyalonema 21 



2. Order HEXACERATINA 21 



Familia Dakwinellid^ 22 



Familia Apltsillid^ 22 



Genus lanthella 22 



Aplysilla 26 



Dendrilla 27 



Familia Halisaecid^ 30 



Genus Bajalus 30 



3. Ordo CHONDROSPONGI^ 32 



Subordo TETRAXONIA 32 



Group LITHISTIDA 32 



Group CHORISTIDA 33 



Tribus Tetradina 33 



Tribus Trianina 33 



Familia Geodidje 33 



Genus Geodia 33 



Isops 34 



Cydonium 36 



Familia Stellettid^ 37 



Genus Stelletta 37 



Psammastra . 38 



Thalassomora 40 



Familia Ancorinidje 41 



Genus Ancorina 41 



