CTDONIUM. — STELLETTA. 3, 



cortex. The greater part of the centripetal ray, and also the tangential rays, 

 are free ; the latter form a kind of veil, which is, as the centripetal rays project 

 about 2'5 millim., that distance away from the surface of the sponge. The 

 measurements of these spicules and their shape are the same as those of the 

 tetract supporting-spicules. The veil produced by these spicules is comparable 

 to analogous structures in certain Hexactinellida. — (3) Monad Supiwrting- 

 Spicides. In the interior, the pulpa, of the sponge, bundles of styli are met 

 with, which consist of 5-7 spicule-series. The spicules are slightly curved, 

 cylindrical, and sharp-pointed at one end ; they gradually taper towards the 

 other rounded end ; these spicules are very long and slender, measuring 

 2 X 0-04 millim. — (4) Monact Sincules of tlie Cortex. In the outermost layer 

 of the cortex dense masses of oxea are found ; these are situated obliquely or 

 perpendicular to the surface ; they are sharp-pointed and slightly curved, 

 measure 0'32x0'012 millim., and resemble the spicules of certain Eenieridte 

 very closely. — (5) Olohostellates. These are very large and oval, or somewhat 

 kidney-shaped ; those in the cortex form dense masses ; they are the largest, 

 appear comparatively smooth, possess an umbilicus, and measure 0-16 millim. 

 in diameter. The globostellates in the interior, where they are numerous but 

 scattered, are smaller and more regularly spherical. Young stages in every 

 degree of development are found here ; these possess dense and sharp spines. 

 The spines when broken off are sharp, regularly conic, 0-015 millim. long, 

 and at the base 0-003 millim. wide. — (6; Stellate Spicules of the Cortex. The 

 outermost layer of the cortex is composed of exceedingly minute stellates with 

 6-10 ravs measuring 0-003-0-005 millim. in diameter; they form a layer about 

 0-05 millim. thick, which is penetrated here and there by the cortical oxea. — 

 (7) Stellates of the Pulpa. Two varieties of stellates are met with in the 

 interior : — (A) Stellates similar to the cortical ones ; these are pretty numerous. 

 (B) Stellates of much larger dimensions, with stout, conic rays 0-03 millim. 

 in diameter ; these are scarce, and it is often difficult to find them. 



Geographical DiSTEisuTioisr. — East coast of Australia {Eamsaij). 



Familia STELLETTID^. 



Trianina with stellate microsclera in the cortex, hut without 

 globostellates. 



Genus STELLETTA. 

 Stellettidce with simple stellate microsclera. 



