BY R. VON LENDENFELD, PH.D. 533 



was dry it is difficult to ascertain whether these cavities are 

 vestibule-lacunae or Oscular tubes. I am inclined to consider them 

 as the former, judging from their similarity with the homologous 

 structures in Euspongia irregularis and canaliculata described 

 above. 



Skeleton. 



The main fibres are straight and not very thick, they contain a 

 greater or smaller amount of foreign bodies. 



The connecting fibres form a regular network, as mentioned in 

 the description of the sub-genus. 



The meshes are regular and small. The average thickness of the 

 fibres is according to F. E. Schultze (I.e., p. 635), 0-03-0-038 mm. 

 It varies according to the varieties. 



I. EUSPONGIA OFFICINALIS CAVERNOSA. 



The skeleton consists of (1), stouter main fibres, which are 

 approximately straight and parallel to each other, about 0"04-0"07 

 mm. apart, more or less vertical to the sui'face (I presume this a 

 mistake, it ought to be 0-4-0 -7 mm.) according to position. Thickness 

 about 003-0"04 mm., and (2) of connecting fibres, similar to the 

 main fibres, and more or less vertical to them, but often very 

 obliquely placed, thickness about 0-013-0 -03 mm. ; distance apart, 

 very variable from 0-14 upwards. 



II. EuSPONGIA OFFICINALIS DURA. 



The main fibres are very thick and pretty close together, 

 being on an average 0-5 mm., apart and measuring 0-2 mm., in 

 thickness. The main fibres of no other variety are so thick. They 

 are completely filled with foreign bodies 80% sand grains averaging 

 0-05 mm., and foreign spicules. These are mostly short fragments. 

 The surface of the main fibres is uneven. The knobs are not high. 



The connecting fibres form a very regular network. The meshes 

 average 0*33 mm., in width. The thickness of the fibres is 0-033 



