674 j;. KiKKrATiucK. 



conules may be roinided at the suinmir, or more elongated thau 

 usual. A little below the surface the uppermost tabnlte are 

 visible, each Avith a central, circular or oval hole or nearly 

 closed slit (PI. 35, fig. 16). Sometimes the tabula is merely a 

 rim or ledge round the inner wall of the calcareous tube, and 

 the central hole is correspondingly large; or, again, the tabula 

 may be imperforate. The tabula? show five or six sutui-al lines 

 radiating from the centi'al hole or slit to the circumference. 



On the surface of the specimen incrusting the Dendvo- 

 phyllia there are numerous small circular holes due to worm- 

 tubes, and here and there among the ordinary meshes of the 

 Merlia are larger ones nearly "S mm. in diameter, with a 

 shallow floor, on Avhich there are radiating ridges and even a 

 central columella-like knob, the whole somewhat resembling 

 a very small coral calycle. The large meshes are here simply 

 due to the effort of the sponge to repair the lesion caused by 

 the presence of the woi'm-tnbes, the openings of Avhich are 

 found just beneath the floors of the supposed calycles. 



A vertical section of the skeleton shows parallel vei tical 

 tubes divided up by tabula (PI. 35, fig. 17). Often the tabula^ 

 form a series of parallel horizontal planes at regular intervals 

 of about "15 mm., but the regularity is frequently disturbed, 

 as will be obvious from fig. 9 on PI. 32, showing the soft 

 tissues Avhich filled the crypts. 



The magnified surface view of the skeleton (PI. 35, fig. 

 16) shows three flanges or wings radiating from the base of 

 each tubercle and meeting opposing flanges from neighbour- 

 ing tubercles. A sutural line marks the junction of the 

 opposing flanges, and the most prominent radial sutures on 

 the tabula? are continuous with those between the flanges. 

 A vertical section sliows the interflange sutures to be con- 

 tinued as vertical lines down the walls of the tubes from 

 surface to base. 



The tabulae are about '01 5 mm. thick. On both surfaces, 

 in addition to the radial sutures there are fine concentric 

 markings confined to those surfaces, the thickness of the 

 tabula being homogeneous. 'The radial sutures typically 



