TETHYA. 49 



marginal couuli ; these make the circumference appear irregular, polygonal. 

 These remarkable rosettes attached to the surface are connected with each other 

 by threads and bands 0-5-2 millim. in breadth, which bridge over the 2-3 

 millim. wide fissures between the rosettes. Spicules protrude from the rosettes 

 to a great length and give the sponge a hairy appearance. Two to four 

 oscula, 1-5 millim. in diameter, are situated on the upper surface. 



Numerous small canals originate from the bottom of the fissures, and join 

 to form inhalant stems, which traverse the cortex and extend to insignificant 

 subdermal cavities at the limit between cortex and pulpa. There appear to be 

 no inhalant pores in the projecting rosettes. Below the inhalant pores there 

 are peculiar chona3-like arrangements for regulating the water-current. In the 

 pulpa irregular canals descending from the subdermal cavities are met with ; 

 some of these extend tangentially in a lacunose manner; sand-grains are 

 observed in their walls. 



SHleton. — The skeleton consists of a hard, spherical, central mass of irregu- 

 larly disposed spicules, which measures 6 millim. in diameter. The bundles 

 which radiate from this centre are 1-1-5 millim. thick, and expand distally in the 

 surface rosettes, where they are surrounded by small monact spicules, and there 

 are two kinds of stellates.— (1) Megasclem. Styli 3 x 0-08-0-1 millim. ; straight, 

 cylindrical, obtusely pointed, the pointed end centripetal ; greatest thickness 

 at the truncate end.— (2) Monact Spicules of the Cortex. Styli surrounding the 

 surface-tufts and projecting, like the spicules in the distal part of the radial 

 bundles, some distance beyond the surface, 0-9 x 0-012 millim., obtusely pointed 

 at the centrifugal end, which projects 0*5 millim. beyond the surface. The large 

 bundle-spicules project 1-2 millim.— (3) Stellate Microsclera. Two varieties : — 

 (A) Large stellates, with conic rays, forming dense masses in the cortex ; body 

 of spicule 0-048 millim. in diameter, with on an average twenty conic sharp- 

 pointed rays 0-08 millim. long and at the base 0-016 millim. thick. (B) Small 

 stellates, with slender, cylindrical rays, \\ Inch are terminally thickened ; these 

 spicules form the outer coating of the sponge, and are also scattered through- 

 out the interior ; they measure 0-01 millim. in thickness. Besides these a 

 great abundance of the young stages of the larger kind of stellate is to be 

 found. 



Geographical Distribution. — East coast of Australia : Port MoUe, 

 Q. {Ramsay) ; Port Jackson, N. S. W. {Ramsay, Lendenfeld). New Zealand 

 {Lendenfeld). 



Tethya inflata, n. sp. 



Spherical sponges, sometimes depressed in the centre, 40 millim. broad and 

 20 millim. high, attached by a broad base. Surface smooth, with very long 

 (30 millim.) and 0-2 millim. thick, thread-shaped appendages, which grow out 



E 



