36 



ISOPS. CYDUKIUM. 



diameter, are covered with long and slender spines. — (i) Pohjact Stellate Spi- 

 cules. There are- two varieties of these spicules scattered indiscriminately 

 throughout the interior of the body :— (A) With numerous short and thick 

 spines, 0-016 millim. in diameter. (B) With comparatively few rays or 

 spines ; the number varies from two to twelve. The rays of these spicules 

 are very slender and thin; they measure 0-014 x 0*0016 millim.; the whole 

 spicule attains a diameter of 0-028-0-03 millim. Young stages of both 

 A'arieties are found in abundance. The small spicules of the slender-spined 

 variety possess more rays than the large ones ; and it is to be supposed that 

 the number of spines decreases with increasing age. 



GrEOGBAPHicAL DISTRIBUTION.— East coast of Australia: Port Jackson 

 {Ramsay, Lendenfeld). 



Genus CYDONIUM. 



Inhalant and exhalant pores similar ; the former generally in a 

 group together. Oscula and pores both over chonse. Globo- 

 stellate and stellate microsclera. 



Cydonium erinaceus, n. sp. 



This sponge is of a rather variable shape. Specimens with thick digi- 

 tate or lobose processes are the most numerous ; massive ones, however, 

 also occur. Large specimens are usually branched ; they measure 200 x 

 100 X 50 millim. The processes are generally situated on the margin of the 

 usually comi)ressed sponge, and are as thick as the sponge itself (50 millim.), 

 and being rounded, dome-shaped, about equally long. Here and there there arc 

 oval depressions in the surface, which measure 8 x 12 millim. ; at their bottom, 

 which lies 3 millim. below the surface, the oscula are situated. The sponge is 

 excessively hard, like a Lithistid. The surface is even, but appears spiny 

 in consequence of the presence of numerous large tetract spicules, which project 

 several millimetres beyond it. Colour in spirit dirty white or light brov\-n. 

 The chon?e are similar to those of the species described by Sollas. The canals 

 which are found in the pulpa mostly exteiid in a centripetal direction : some 

 are wide and irregular, having a diameter of 2 millim. ; a greater number 

 are more regular, and have a diameter of about 0-6 millim. 



Sl-eleton. — (1) Tetract Supporting -Spicules. Abundant below the cortex. 

 Angle between centripetal and tangential rays = 100" ; centripetal ray 

 straight, conic, pointed, 1-3 X 0-04 millim. ; tangential rays curved, concave 

 towards the interior; all of equal size and with equal angles, 0-4 x 0-03 

 millim., conic, not sharply pointed. — (2) Tetract Velar Spicules. These are 

 attached by tlieir centripetal ray, «hieh is planted in the outer part of the 



