52 TETHTA. — TETHTOKnilAPHIS. 



with sharp conic raj^s ; abundant in the surface, but very scarce in the interior. 

 (B) Small stellates, with slender, cylindrical, terminally thickened rays, forming 

 a dense layer on the outer surface and scattered throughout the interior, parti- 

 cularly in the walls of the canals. (C) Small stellates, without any visible 

 central body, and with slender, spined, conical rays, 0-04 millim. in diameter. 



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

 N. S. W. (Ramsay). 



Genus TETHYORRHAPHIS, u. gen. 

 Tethydae with small diact microsclera, besides the stellates. 



Tethyorrhaphis Isevis, n. sp. 



Spherical sponges, 30-45 millim. in diameter, sometimes higher than broad, 

 attached by a small base ; without rootlets ; occasionally with short irregular 

 outgrowths around the base of attachment. Surface slightly tubercular in 

 some parts of the sponge, even and smooth in others ; the tubercles are separ- 

 ated by rounded concave depressions, and project not over 1 millim. In spirit 

 light brown on the outer surface, the interior of a lighter colour. 



Just below the surface extensive laterally extended, tangential canals, 

 0-2 millim. in diameter, are met with. The inhalant pores are situated in 

 zones over these canals ; from them the usual centripetal canals originate, 

 which often divide into two or more branches before they leave the cortex ; 

 anastomoses between them occur very rarely. The cortex is 2 millim. thick, 

 below it we find irregular canals from 0-05 to 0-17 millim. in diameter 

 pervading the pulpa. Eadial canals are rare. The oscula are small, and 

 scattered over the upper surface. 



Skeleton. — The bundles which radiate from the centre of the sponge have 

 a thickness of 0-5-0-8 millim. ; they expand distally to form the usual 

 surface-tufts. Diact and stellate microsclera are abundant in the cortex 

 and pulpa. — (1) Megasdera. Strongyla 2x0-036 millim., spindle-shaped, the 

 greatest thickness (0-036 millim.) about 0-5 millim. from the centripetal end, 

 which is about four times as thick as the distal ; both ends are rounded ; 

 the distal rays project 0-2 millim. beyond the surface. There are no smaller 

 cortical spicules surrounding the surface-tufts. — (2) Stellate Microsclera. 

 There are three varieties of stellates : — (A) Spherical, large spicules, 

 with conic rays 0-064 millim. in diameter, fairly abundant just below 

 the surface and along the inhalant canals, but very scarce in the interior. 

 (B) Small stellates, with slender cylindrical terminally thickened rays, 

 0-012 millim. in diameter, scattered throughout the interior, pretty scarce. 



