80 ART. 7. — I. IJIMA : HEXACTINELLIDA, IV. 



than two openings. Thus the canals in question are strictly 

 comparable in character to the intercanals of the Ascons, and 

 indeed the species bears some external resemblance to certain of 

 those Calcarea. Needless to say the above perforating passages, 

 for which the name intercanal may be borrowed, are throughout 

 lined with the dermal layer as is of course the entire surface 

 externally exposed {vide PI. YI., fig. 7, in which the dermal 

 surface is colored yellow). 



The external depressions are on the whole deepest, and the 

 intercanals most frequently developed, in the lower part of the 

 bodv. In that re2;ion the thickness of tlie bodv-wall — consider- 

 ing this to be represented by the space between the general 

 surfaces of the exterior and of the central gastral cavity — must 

 be said to be considerable, being 90 mm. or more in very large 

 specimens. But, if we restrict the application of the term 

 " body-wall " to that layer of the sponge-tissue which is bounded 

 externally by the dermal layer and internally by the excurrent 

 surface, irrespective of whether the latter belongs to the gastral 

 cavity or to the canals opeining into it, the wall-thickness is 

 nowhere very great, being usually 2-3 mm. and probably never 

 more than 5 mm. 



Apart from the external irregularities above described, the 

 dermal surface is smooth. The dermal layer is of an extremely 

 delicate kind. The hypodermal lattice-work is made up of beams 

 which are so fine as to be barely discernible with the naked eye. 

 The closely set incurrent apertures, visible through the dermal 

 layer, are small, measuring not more than 2 mm, iu diameter. 



The gastral surface (PI. VI., fig. 7) presents an appearance 

 essentially similar to that of C. meijeri. Above and near the 

 oscular margin, there occur only small roundish excurrent aper- 



