REVISION ''BRITISH SPONGIAD^." 258 



Baspailia ramosa, Mont., XVI. 



,, rectangula, B., LXXXIV. 



ve7itilabric7n,B.,XVl. (Hanitsch, 8,p.212.) 

 ,, virgultosa, B., XIX. 



Genus Acarnus, Gray. 

 Megascleres of the ectosome diactinal (tylota) ; those 

 of the choanosome monactinal (smooth styh). Accessory 

 megascleres of the choanosome cladotyles, characteristic 

 of the genus. Microscleres isochelse and toxa. 

 Acarnus stelliferus, B., XXVII. 



Genus Pytheas, Topsent {18, p. 110). 

 Megascleres of the ectosome usually spined styli, lying 

 tangentially. Skeleton of the choanosome formed of 

 bundles of smooth diactinals, echinated by spined styli. 

 Isochelae usually present. 



Pytheas inflatiis, B., LXXIX. 



Genus Spanioplon, Topsent {18, p. 116). 

 Chief megascleres of the choanosome smooth mon- 

 actinals, few in number as compared with the megascleres 

 of the ectosome, smooth diactinals. With accessory 

 small spined spicules (microxea, microstyles, or tylostyles). 

 Microscleres (isochelse and sigmata) rarely present. 

 Spanioplon armaturum, B., XXXIV. 



Genus Clathria, 0. Schmidt. 

 Main skeleton formed of well-developed horny fibres 

 cored with smooth styH, echinated by spined styh. No 

 special dermal skeleton. Microscleres isochelae and (or) 

 toxa, sometimes absent. 



Clathria heani, LVIII. 



davigera, B., XXXVII, 

 ,, laciniosa, B., LXXV. 

 Genus Clathrissa, Lendenfeld, emend. {11, p. 217). 

 Main skeleton formed of dense bundles of diactinals, 

 with very httle spongin, echinated by spined styli. With 



