4 Proceedings of the Royal Society of Victoria. 



conical and gradually sharp-pointed and measure about 0072 

 by 001 mm. The basal ray may be of about the same 

 length or shorter or longer than the others, and is perhaps 

 generally directed somewhat downwards towards the base 

 of the sponge ; ('^) On the surface of the sponge, outside 

 the giant oxeote spicules, is a layer of ver}^ minute oxea 

 arranged at right angles to the surface and hence also at 

 right angles to the large oxea, and each with one end 

 projecting very slightly, if at all, beyond the ectoderm. 

 These oxea are very slender, measuring at most about 07 

 b3- 003 mm. They are very gradually sharp-pointed at 

 their inner ends and somewhat hastately sharp-pointed 

 at their outer ends. They are straight or only slightly 

 curved. 



The Tvbar Skeleton.— The tubar skeleton is articulate 

 and thus differs from that of Ute argcntea. It is composed 

 of sagittal tru'adiates arranged according to the usual S3'Con 

 plan, and the number of joints depends, of course, upon the 

 length of the chamber ; sometimes there may be as many as 

 a dozen. The sub-gastral sagittal tru-adiates, forming the 

 })roximal joint of the skeleton, are, as usual, rather difterent 

 in sha]:>e from the remainder of the sagittal spicules consti- 

 tuting the tubar skeleton. The oral angle is nearly 180°; 

 the oral rays are slightly curved awa\' from one another 

 towards the basal ray, the}" are conical, gradually sharp- 

 pointed, and measure about 084 by 001 mm. The basal 

 ray is straight, conical, very gradually sharp-pointed, 

 measuring about 01 4 by 001 mm. There is a more or 

 less gradual transition between these sub-gastral sagittal 

 triradiates and the more distallj- placed spicules of the 

 tubar skeleton. The oral rays first become approximately 

 straight and spread out nearly at right angles to the basal 

 ray ; then, further awa}" from the gastral cavity, they begin 

 to curve towards one another away from the basal ray, and 

 the oral angle is somewhat reduced. At the .same time the 

 basal ray becomes shorter, until it is only about the same 

 length as the orals (now about 007 mm.) All the rays still 

 remain conical and gradually sharp-pointed. 



The GcLstral Skeleton. — This consists of quadrii-adiates 

 and triradiates, backed by the oral arms of the sub-gastral 

 sagittal triradiates. The quadriradiates are stout sagittal 



