nV K. F. HALLMANN. 287 



into chones. Microscleres absent. The me,2:ascleres are of two 

 kincls^the larger, monactinal (typically sul^tylostrongyla): the 

 smaller, diactinal (oxea). The skeleton of the interior, consist- 

 ing chiefly of longitudinal spicule-biindles and variously oriented 

 scattered spicules, is supplemented in the axial region by a reti- 

 culation of fibres composed of a sponginous substance, and in the 

 extra-axial region by radiating spicule-fibres, which continue iuto 

 the cortex. 



SoLLASELLA DIGITATA. (Plate XV., figs.1,2; and text-fig. 1). 



The species is represented by the incomplete type-specimen 

 (PI. XV., fig 2), by a correctly labelled fragment from the British 

 Museum, and by an entire specimen (PI. xv,, fig.l) from an un- 

 known locality, probabh^ obtained by the " Thetis " Expedition. 



External features. — Sponge ramose, stipitate ; stalk and 

 branches short, stout and cylindrical, the latter extending up- 

 wards and outwards in various directions without anastomosis. 

 Surface even, very sparsely hispid with singly dispersed long 

 spicules that project 2 or 3 mm. beyond it, and conspicuously 

 characterised by a polygonal areolation formed by lines of uni- 

 serially disposed, closely approximated, small shallow pits; these 

 pits are terminated below by a microscopically cribriporal mem- 

 brane, which roofs over an inhalant chone. The oscula are few, 

 scattered, small; they measure up to 2 mm. in diameter. Con- 

 sistency very firm, dense, and tough. Colour in alcohol brownish. 



In one of the specimens (PI. xv., fig.2), the surface-areolation 

 is generally hexagonal, the areolae average between 2 and 3 mm. 

 in width, and the pore-pits, which are usually elliptical in out- 

 line, measure from 0*2 to 0*5 mm. in their longer diameter. In 

 the other, the type-specimen, the areolae are, as a rule, much 

 elongated in the longitudinal direction of the branches, but are 

 very variable in length, and measure only 1 to 2 mm. in width; 

 while, at the same time, the pits are comparatively small, being 

 rarely as much as 0*2 mm. in diameter. Neither of the speci- 

 mens affords any particular justification for Lendenfeld's state- 

 ment that the polygonal fields (areolas) are " expressions of the 

 terminations of the surface-tufts of the spicule-bundles " ; nor do 



