288 A MONOGRAPH OP THE AUSTRALIAN SPONGES, 



These fibres are completely filled with coarse sand and appear 

 as sand fibres which are enclosed by a thin horny layer only. These 

 fibres consequently have a very uneven, knobby surface ; because 

 the outer horny layer is so thin, that it is not sufficient to fill the 

 depressions between the adjacent projecting corners of the sand- 

 grains. The covering horny layer shows a very marked stratifica- 

 tion, consisting of diflPerent layers of horny substance with different 

 refracting powers. These main fibres are on an average 0-3 mm., 

 thick and 1-5 — 2-5 mm., distant from one another. 



The connecting fibres are free from foreign bodies and very much 

 thinner. They attain about one tenth of the thickness of the main 

 fibi-es. They are generally vertical on the main fibres, straight 

 and unbranched. Sometimes it appears as if one of these fibres 

 had several distinct roots, connecting it with the main fibre. It 

 also may happen that two adjacent fibres coalesce half-way 

 between the main fibres for a short distance. Only in this way do 

 some of these fibres appear slightly ramified. The average distance 

 of these fibres from one another is equal to the thickness of the 

 main fibres. 



The genus is found thi'oughout the Australian region. 



59 SPECIES. 



HALME NIDUS VESPARUM, NOVA SPECIES. 



HOLOPSAMMA LAMIN/E FAVOSA. Carter (1). 



Plates XXVI. , XXIX. 



Shape. 



A great many sponges of very varying shape, which I have seen, 

 correspond in their internal structure so closely, that I have com- 

 bined them to the above species. 



According to my idea a great many sponge specimens, which 

 have passed through my hands belong to it, 



vl) H. J. Carter. Description of sponges from the neighbourhood of 

 Port Phillip Heads continued. Annuals and Magazine of Natural History, 

 Series 5, Vol. XV.. page 212. 



