92 I. IJIMA : HEXACTIXELLIDA. I. 



equal to that of an ordinary watch-glass. More frequently it 

 presents a stronger arching, being often of the shape of a hemi- 

 spherical vault. The meshes are smaller than in E. imperialis 

 and never exceed 4 mm. in their greatest width ; they have 

 mostly a shape varying from oval to triangular or polygonal, the 

 corners in the latter cases being invariably rounded. The beams 

 are comparatively strong-looking and are distinctly laterally com- 

 pressed like those of E. aspergillum or E. oweni. Seen from 

 above, the majority are less than 1 mm. or even half a millimeter 

 in width ; but the same beams, when seen from the sides, may 

 be considerably wider, up to nearly 2 mm. in the case of a 

 strong beam. Towards the nodes, as seen from above, the beams 

 either maintain their width uniformly or broaden so as to form 

 a more or less distinct nodal thickening. Occasionally a beam 

 or a node is so broad (up to 3 mm.) as to deserve to be called 

 plate-like. A distinction of the meshes into the greater and the 

 lesser — the former bounded by wider beams and containing a 

 number of the latter — can not be made in the present species. 

 The surface of the sieve-plate beams is on the external side 

 close-grained and compact-looking, while on the inner side are 

 seen small excurrent openings scattered between separate strands 

 of fibers. 



The lower end of the sponge-body (PI. IV, fig. 5) is likewise 

 closed by a perforated plate, the bottom-plale (see p. 40). Though 

 often found in a damaged condition, the occurrence of this plate 

 seems to be constant in the present species. It is a direct conti- 

 nuation of the lateral parietes ; thin, measuring not more than 

 about IY2 mm. in thickness; tolerably even on both surfaces; 

 and nearly flat or outwardly convex. The skeletal framework 



