1886.] POSITION AND CLASSIFICATION OF SPONGES. 575 



II. Ordo HEXACTINELLIDA, O. Schmidt. 



Schulze (1369) divides the living Hexactinellida into the two 

 Suborders Lyssacina and Dictyonina of Zittel. In the first, the 

 spicules remain isolated or coalesce secondarily in an irregular 

 manner ; in the second, the main spicules coalesce to begin with in 

 a very regular manner, so as to form a continuous scaffolding. In 

 the first suborder Lyssacina, the famihes Euplectellidse, Gray, 

 Asconematidse, F. E. Schulze, Rossellidte, F. E. Schulze, and 

 Hyalonematidse, Grray, are placed. The second suborder, Dictyonina, 

 comprises the families Farreidae, Gray, Euretidae, F. E. Schulze, 

 MelittionidBe, Zittel, Coscinoporidse, Zittel, and Meandrospongidse, 

 Zittel. To these the fossil families Ventriculitidse, Staurodermidse, 

 Callodictyonidse, Cceloptychidae, Receptaculitidse, and Monakidse 

 must be added. 



In the classificatory scheme below, Schulze's diagnoses are 

 translated. 



III. Ordo CHONDROSPONGI^, Lendenfeld. 



As mentioned above, this Order coincides nearly with Vosmaer's 

 (1550) order Spiculispongiae. I divide it into the two groups, 

 Tetraxonia and Monaxonia. The former comprises the Sponges 

 with tetraxon spicules, Tetractinellids and Lithistids ; and the latter 

 those forms which have monaxon spicules, or which have no spicules 

 at all. 



Sollas (1453) divides the Tetraxonia into two groups : — Choristida, 

 Sollas, without lithistid sclerites; and Lithistida, Zittel, with 

 lithistid sclerites. In the first group the families Plakinidse, 

 Pachastrellidse, Corticidse, Tetillidse, Theneidse, Stellettidse, and 

 Geodinse are distinguished. 



Vosmaer (1550) divides the Lithistidae, in accordance with Zittel 

 (1639) and O. Schmidt (1306, 1322), into the families Rhizomori- 

 nidae, Megamorinidse, Anomacladinidse, Tetracladinidse. 



The Monaxonia comprise the families Siiberitidae, Spirastrellidse, 

 Tethydae, and Chondrosidae. The Clavulina and portion of the 

 Oligosilicina of Vosmaer. 



IV. Ordo CORNACUSPONGIiE. 



I divide the Cornacuspongiae into the two suborders Halichondrina 

 with, and Ceraospongiae without, proper spicules in the supporting 

 skeleton. 



The Halichondrina comprise the three families Homorhaphidae, 

 Heterorhaphidae, and Desmacidonidae of Ridley and Dendy (1265, 

 1266). 



The Ceraospongiae are divided by me into two groups — Macro- 

 camerse with large, and Microcamerae with small, ciliated chambers. 

 To the former belong the families Aplysillidae and Spongelidae, and 

 to the latter the Spongidae, Aplysinidae, and Hircinidae. 



After this general view of the Classification of Sponges, I shall 

 proceed to give a " system " of Sponges down to subfamilies, 

 mentioning the principal genera in each group. 



