i6 



V. GEOGRAPHICAL AND BATHYMETRICAL DISTRIBUTION 



OF PLACOSPOXGIA. 



Atlantic. — Gulf of Mexico, Florida '(Schmidt). — Puntas Arenas (Carter). — W. Coast of 

 Portugal (Hanitsch). — Adriatic (Buccich, Lendenfeld). 



Pacific. — "South Sea" (Bowerbank). 



INDIC. — Mahé (Wright). — Gulf of Manaar (Carter). • - Ceylon, Bass Rocks (Carter). — 

 Gulf of Aden, Tadjoura (Topsent). — Red Sea (Keiler). 



INDIAN ARCHIPELAGO. — Borneo (Gray). — Ternate (Kieschnick). — Amboina (Topsent). — 

 Strait of Casper (Lindgren). — Celebes (Thiele). — Torres-Strait (Ridley). — Straits of 

 Malacca (Bowerbank). — Flores Sea (Siboga-Expedition Stat. 43, 213). — Sulu Sea (Siboga- 

 Expedition Stat. 99). ■ Arafura Sea (Siboga-Expedition Stat. 164, 273). — Banda Sea 

 (Siboga-Expedition Stat. 240, 250). 



The greatest depth wherein Placospongia is found reaches 1 1 7 M. (?), according to 

 Carter; several are found in shallow water. The largest quantity is found by the Siboga on 

 the W. Coast of New Guinea (Station 164) in a depth of 36 M. 



Whereas Placospongia decorticans is found in the Adriatic and on the W. Coast of Portugal, 

 P. carinata and P. melobesioides occur in the tropics between 30° N. and 20 S. of the aequator. 



VI. SYSTEMATIC POSITION OF THE GENUS PLACOSPONGIA. 



Well aware of the peculiarities of Placospongia, Gray l ) created for the nevv genus, 

 the family Placospongiadae (1867 p. 549). He placed this family as nearest related to the 

 Geodiadae under the order Sphaerospongiadae. Many authors, Schmidt, Sollas, Topsent, 

 Hanitsch and even Minchin (1900 p. 148) believe in the close relation of Placospongidae 

 and Geodidae. Carter however, suggested, (1875 p. 198) that they were nearer to the 

 Suberitidae. Keller (1891c;) was the first to demonstrate that the "sterrasters" of Placo- 

 spongia develop from "spirasters" and he placed the genus therefore to the "Spirastrellidae." 

 Herein he is foliowed in the main points by Lendenfeld, Thiele, Kieschnick and Delage 

 (1899 p. 170). It seems to us that there can be no doubt that Placospongia has nothing to do 

 with Geodidae, that it does not belong to the Tetractinellida but to the Monactinellida, probably 

 near to the Clionidae. The difinition of the genus may then be : Sponge incrusting or branching; 

 the branches consist of a solid axis of sterrospirae, around which lies the soft parenchyma. Cortex 

 hard, chiefly composed of sterrospirae. Stomata and procts situated in cortical grooves, which 

 are destitute of sterrospirae. Spicula : i° parenchymal tylostyles in radiating bundies ; 2" cortical 

 tylostyles at right angles to the surface; 3" sterrospirae; 4" the dermal spiculum is a spherule 

 or a microspira ; 5" parenchymal spinispirae in some species ; 6" spherasters in some specimens. 



1 Cray (1867) was the first, not Sollas (1SS8) as Lendenfeld (1S94.5 p. 114) erroneously suggests. 



