DENDY— HOMOSCLEROPHORA AND ASTROTETRAXONIDA 231 



I identify with this species a plate-Hke fragment of considerable size, about 58 mm. 

 in length, 45 mm. in breadth and 8 mm. in thickness. The plate is slightly curved and one 

 surface bears small, thickly scattered pore-sieves, while the other bears numerous small, 

 scattered oscula, less than 1 mm. in diameter and with their margins level with the general 

 surface. The margin of the plate, where intact, is broadly rounded, but the incurrent face 

 ends sharply above in a well-marked edge. Part of this edge only is provided with a 

 fringe of long projecting oxea and both surfaces are also hispid in places. 



The broken edges show the narrow inhalant and exhalant canals running through the 

 plate more or less at right angles to the two surfaces. 



The colour in spirit is dull, pale yellow ; texture firm and harsh, but rather friable. 



The skeleton is an extremely confused feltwork of large oxea. There are also 

 numerous very long and very slender oxea which are chiefly arranged in loose fibres or 

 wisps, which run towards the surface and in places project therefrom in long loose 

 bundles. The comparatively few tetract spicules appear to be quite irregularly scattered 

 through the sponge. 



Spicules. (1) Calthrops and short-shafted trisenes (Plate 45, fig. 2 a), not sharply 

 distinguishable from one another. Rays sharp-pointed or rounded, about 0'5 mm. long by 

 0*05 mm. in diameter at the base. The rays are sometimes slenderer. These spicules are 

 not numerous and they rarely show any reduction of rays, but irregularly branched forms 

 are occasionally found. 



(2) Stout, fusiform, slightly curved and sharply pointed* oxea (fig. 2 h), measuring 

 about 3"0 by 0"05 mm. Sometimes reduced, by rounding off" of one or both ends, to styli 

 or strongyla (figs. 2 c, 2 d). Shorter oxea also occur. 



(3) Long, hair-like oxea (fig. 2 e), of about the same length as the largest but only 

 about O'OOS mm. thick. Very numerous and commonly arranged in loose wisps. 



(4) Slender-rayed metasters (fig. 2/), with about six or eight long rays or spines. 

 Greatest length of entire spicule usually about 0'016 mm. 



(5) Microxea (fig. 2 g) ; slender, slightly curved, sharply pointed ; with very slight 

 indications of roughening ; size about 0"15 by 0"004 mm. Rather scarce. 



I have in my possession several of SoUas's original preparations of Pachastrella 

 {Pcecillastra) tenuilaminaris and a careful comparison of these with the "Sealark" 

 specimen seems to me to justify a specific identification. The chief apparent difierences 

 are as follows. 



(1) The "Challenger" specimen had no special hispidating fringe at the margin. 

 This is of little importance. 



(2) The long hair-like oxea are not mentioned in SoUas's description. They are 

 certainly very rare hi the " Challenger " material, but I have seen a few. 



(3) The tetract spicules are less numerous in the "Sealark" specimen ; they show no 

 tendency (so far as observed) to regular arrangement at the margin, as in the "Challenger" 

 specimen. 



(4) Reduced tetracts with only one ray are common in the " Challenger " material. 

 I have never seen them in the " Sealark " specimen. 



* SoUas's statement that the oxea are not sharply pointed is not borne out by his preparations. 



