42 ANCOEINA. — SPIBETTA. 



Skeleton. — (1) Tctract Spicules of the Su/pportincj-Slceleton. Thetetract spicules 

 form two layers in the cortex and are also scattered throughout the pulpa of 

 the sponge. Between the tufts which form the outer layer, and which expand 

 tov\'ards the outer surface, small tangential subdermal canals are met with. 

 Below these another layer of similar spicules is situated. Angle between the 



centripetal and tangential rays = 90° ; centripetal ray straight, conic, sharp- 

 pointed, 1"4 X 0-021 millim. ; tangential rays either short and strongly curved — 

 angle between them and the centripetal may <: 90°, or long and only slightly 

 curved, this angle > 90° — conic, pointed; the tangential rays are 0*024-0-15 

 millim. long, and at the base 0-02 millim. thick. The tetracts in the interior 

 are similar to these, but more slender. — (2) Tetmct Velar Spicules. These 

 spicules are attached to the outer surface and give it the hairy appearance 

 mentioned above. As far as their shape and dimensions are concerned they 

 resemble the spicules with the long tangential rays, described above, of the 

 cortex ; they project 1 millim. beyond the surface. — (3) Monact Spicules of the 

 Interior. Oxea nearly straight, sharp-pointed, 1-2 x 0-016 millim., in bundles 

 and scattered ; some of these spicules in the interior of the sponge possess 

 irregular excrescences. Monact spicules of the same dimensions are also found 

 in tlie surface-tufts. 



Geourapuical DiSTMBUiioN, — East coast of Australia : Port Jackson 

 i^luimsaij). 



Tamilia THENEID^. 



Triaiiiiia with large efferent pores to the cihated chambers, and 

 spiiastrelUd microsclera. 



i\o specimens in the Australian Museum. 



Familia TETILLID^. 

 Triaiiina with sigmate, spiral, or rod-shaped microsclera. 



Genus SPIRETTA, n. gen. 



Ancorinidee without a fi])re-cortcx, with projecting tetract velar 

 spicules, and monact microsclera, but no stellates, with abundant 

 small spiral microsclera. 



