16 A MONOGRAPH OF THE 



central line of grains of extraneous matter within the 

 fibres. 



Stematumenia, Bowerbank. 



Skeleton. Primary fibres solid, more or less compressed, 

 containing a central axial line of spicula and grains of 

 extraneous matters. Interstitial structures abundantly 

 fibro-mernbranous. Vol. I, pp. 211, 77, 66. 



Types. Undescribed species in the cabinet of the author. 

 Vol. I, Plate XII, Pig. 256, and Plate XXXVII, Pig. 

 381. 



Suborder VII. Irregular and entirely areno-fibrous skele- 

 tons. Skeleton irregularly areno-fibrous, having the 

 skeleton -fibre filled from the centre to the surface 

 with grains of extraneous matter. 



Dysidea, Johnston. 



Skeleton. Primary and secondary fibres principally irre- 

 gularly areno-fibrous, occasionally regularly areno- 

 fibrous. Secondary fibres, when destitute of extraneous 

 matters, frequently tubular. Vol. I, p. 211. 



Type, Dysidea fragilis, Johnston. Vol. I, Plate XIV, 

 Pigs. 270, 271, 272. 



