574 DR. R. VON LENDENFELD ON THE SYSTEMATIC [DeC. 21, 



1. Ordo CALCISPONGIiE, Blainville. 

 The only Order, with the characters of the Subclassis. 



11. Subclassis SILIOEA, Lendenfeld. 

 Spongise with a skeleton composed of siliceous spicules and their 

 descendants with horny aspiculous skeleton and askeletous forms. 



2. Ordo HEXACTINELLIDA, O. Schmidt. 

 Silicea with soft mesogloea. Supporting skeleton often strengthened 

 with siliceous cement. Spicules triaxon. 



3. Ordo CHONDROSPONGIiE, Lendenfeld. 



Silicea in which the toughness is achieved by the mesogloea or 

 mesodermal ground-substance becoming cartilaginous, whilst the 

 spicules remain isolated. Spicules tetraxon, monaxon (tylostylus), 

 or absent ; generally corticate. 



4. Ordo CORNACUSPONGI^, Vosmaer. 



Silicea with soft mesogloea or mesodermal ground-substance ; the 

 supporting skeleton, composed of bundles of monaxonid not tylostyle 

 spicules, is strengthened by spongin, which cements the spicules. 

 These may disappear altogether, and the skeleton is then composed of 

 spongin with or without foreign bodies. The skeleton rarely dis- 

 appears altogether. 



Having thus divided the Class Spongise into four Orders, we may 

 proceed to the further division of the Orders into Families. 



I. Ordo CALCISPONGIiE, Blainville. 



This Order has been divided by Hiickel (627-629) into the well- 

 known three families Ascones, Leucones, and Sycones, with seven 

 genera in each. Polejaeflf (1179) has divided the group into two 

 Suborders and replaced Hackel's genera by the older and wider 

 genera of Grant and others. I (888) have tried to combine Hackel's 

 and Polejaeff's classifications, and have added three new families to 

 the existing ones. 



I have retained Polejaeff's terms for the two Suborders, but have 

 altered their meaning. In some Calcareous Sponges the whole of 

 the entoderm consists of collar-cells. There are no entodermal 

 pavement-cells in these forms. These constitute my first Suborder 

 Homocoela. In others the collar-cells are found in the ciliated 

 chambers only, while the central gastral cavity is clothed with 

 entodermal pavement-cells. I combine these forms in the Suborder 

 Heteroccela. 



To the Homocoela belong besides Hackel's Asconidae, my famiHes 

 Homodermidse and Leucopsidse. I acknowledge Hackel's seven 

 genera of the Asconidae. 



In the Heteroccela, Hackel's famihes Leuconidae and Syconidse 

 together with Carter's Teichonidse and my family Sylleibidee are 

 placed. 



