THALASSODENDEON. — PLECTISPA. 225 



irregularly disposed styli, 0"3 millim. long and O'Oll millim. thick, are observed ; 

 these are more abundant in the main than in the connecting-tibres. The 

 fibres are echiuated by two kinds of spicules : — (1) smooth styli, O'l millim, 

 long and 0-007 millim. thick ; (2) spined styli, 0*08 millim. long and 0-006 

 millim. thick. Both kinds are scarce. Very abundant spicules, similar to those 

 in the fibres, are found scattered throughout the ground-substance. 



Geogeaphical Distbibution. — East coast of Australia : Port Jackson, 

 N. S. W. {LendenfeU). 



Thalassodendron brevispina, n. sp. 



Large branched sponges, with very irregular digitate processes. 



The skeleton consists of mostly longitudinally disposed irregular main fibres , 

 0-07-0-15 millim. thick, which are joined by short and simple connecting- 

 fibres, 0-05 millim. thick ; in some places they approximate and coalesce to 

 form perforated plates. In the main fibres a very regular axial bundle, 0-03 

 millim. thick, of spicules is observed. There are no spicules in the connecting- 

 fibres. The spicules in the main fibres are styli, 0-02 millim. long and 0-009 

 millim. thick. Small rough styK, 0*05 millim. long and 0-005 millim. thick, 

 are observed protruding at right angles from the axial spicule-bundle. These 

 are evidently homologous to the echinatiug spicules of other species, but most 

 of them do not protrude beyond the surface of the spongin-cortex of the fibres, 

 which are not echinated accordingly. 



Geogeaphioal Disteibution. — East coast of Australia (Bamsay). 



Thalassodendron viminaliS) n. sp. 



The sponge consists of a number of pretty regularly cylindrical upright 

 branches, which are not much branched. The sui'face is rough or slightly conu- 

 lated, but not grooved. 



The skeleton consists of mostly longitudinally disposed fibres, 0-08 millim. 

 thick, which contain rather scarce, slightly cui'ved, blunt styli, 0*14 millim. long 

 and 0*006 millim. thick. The fibres are echinated by very scarce smooth styli, 

 0-5 millim. long and 0-005 millim. thick. 



Geogeaphical Disteibution. — East coast of Australia : Illawarra, N. S.W. 

 (Bamsay). 



Genus PLECTISPA, n. gen. 



Elegantly reticulate Desmacidonidae, the fibres of which contain 

 only few spicules. The superficial fibres are always echinated on 



