6 Porifera. 



mere membrane (4 Genera; 2 new). The Samidae are characterised by amphi- 

 triaenes (I Genus). To the Asterophora belong the 5 families: Theneidae 

 with spirasters or amphiasters, oxy asters or rnicroxeas ; no cortex ; collenchyme ; 

 chamber-system eurypylous (8 Genera, 4 new) . Pachastrellidae with calthrops, 

 notriaenes; spirasters, spherasters or microrabds ; sarcenchyme ; chamber-system 

 aphodal (3 Genera, 1 new). Stellettidae with euasters, oxeas and triaenes ; 

 chamber -system aphodal; sarcenchyme (16 Genera, 8 new). Geodiidae with 

 sterrasters and triaenes; cortex highly developed; chamber- system aphodal 

 (7 Genera). Placospongidae with sterrasters, but without triaenes (1 Genus). 

 The Microsclerophora may be divided as follows: Placinidae with asters 

 and candelabra; chamber-system either eurypylous or aphodal; collenchyme 

 (2 Genera) . Corticidae with asters and candelabra ; chamber-system aphodal or 

 diplodal ; sarcenchyme and chondrenchyme (4 Genera, 3 new) . Thrombidae with 

 trichotriaenes ; ectosome thin; collenchyme; chamber-system diplodal. The 

 Lithistida are divided into 2 suborders: 1) Hoplophora (provided with special 

 ectosomal spicules ; usually some form of microsclere) , 2) Anoplia (no ectosomal 

 spicules, and no microscleres) . The Hophlophora contain 6 families: Tetra- 

 cladidae with triaenes and m'icroscleres ; the desma is tetracrepid; chamber- 

 system aphodal (8 Genera, 1 new). Corallistidae with triaenes and microscleres; 

 the desma is monocrepid, tuberculated ; chamber -system aphodal (5 Genera, 

 2 new). Pleromidae with triaenes and microscleres; the desma is monocrepid, 

 smooth; chamber -system aphodal ^2 Genera, I new). Neopeltidae, ectosomal 

 spicules are monocrepid discs (1 Genus). Scleritodermidae, ectosomal spicules are 

 microstrongyles ; sigmaspires (2 Genera). Cladopeltidae, ectosomal spicules are 

 monocrepid desmas; no microscleres (1 Genus). To the Anoplia belong 2 fa- 

 milies : Azoricidae with monocrepid desmas (9 Genera, 2 new) and Anomocladidae 

 with acrepid desmas (1 Genus). - - Distribution. A11 the stations from which 

 Tetractinellida have been obtained are situated, quite irrespective of depth, at 

 no great distance from land. The same is true for Monaxonida. In the Indo- 

 Antarctic region were found 7 species (28 dredgings), in the Atlantic 15 (129 

 dredgings) and in the Pacific 42 (120 dredgings), which is about 1:2:3. Most 

 species (41) of Tetractinellids are found between 50-1000 fathoms, 16 were 

 found under 50 fathoms and 8 above 1000. - - In an appendix some Monaxo- 

 nida are described, the position of which S. finds difficult. In (') Tethya appears 

 frankly as Monaxonid and Tetractinellid , in ( 2 ) as Monaxonid , with an adverse 

 criticism on Vosmaer's views. The Monaxonida are divided into : 1) Asemophora 

 (the single family Homoraphidae). 2) Meniscophora (microsclere. when present, 

 usually a sigmaspire, sigma or chela, never an aster). 3) Spintharophora (micro- 

 sclere, when present, an aster). 



Histological details of spicules of Craniella carnosa, see Noll. 



C. Oligosilicina. 

 See Sollas (', 2 , supra, p 4 and 5. 



D. Pseudotetraxoninn. 

 See Sollas (', 2 , supra, p 5 and 6. 



E. Clavulina. 



See Sollas (', 2 ), supra, p 5 and fi. 



According to Topsent ( 2 ) there are in Luc (Coast of Calvados, Channel) 3 spe- 

 cies of Cliona (celata, vastifica, lobata . The first appears in 3 forms: perforante, 



