EEPOET ON THE TETEACTINELLIDA. 
433 
straight or somewhat curved, stout, abruptly pointed, 2*25 by 0'06 mm. 2. Oxea of 
the cortex (PL XLIII. fig. 3), cylindrical to fusiform, straight or curved, abruptly 
pointed, 0‘556 by 0'013 mm. 3. Microxea of the cortex and choanosome (PI. XLIII. 
fig. 4), cylindrical, straight, abruptly pointed, 0'125 by 0‘004 mm. 
II. Microsclere. 4. Amphiaster (PI. XLIII. figs. 5-7), axis ehort, cylindrical; 
actines in terminal whorls, none in continuation of the direction of the axis; 0'007 by 
0’003 mm. 
Colour. — Greyish- white. 
Hahitat. — Bahia. 
Remarks . — The single specimen of this sponge is a fragment of a more or less cake- 
like mass, with one surface flattened, and the opposite irregularly undulating ; it measures 
113 mm. in breadth by 120 mm. in length and 65 mm. in thickness. The fractured 
surface seems to have passed through the middle of the sponge, and reveals the coarse 
spicular fibres which radiate somewdiat spirally from an excentric node towards the surface, 
beyond which the component spicules project for about 0‘4 mm., forming the first line 
of defence of the cortex (PL XLIII. figs. 8, 9) ; between these are packed the oxeas of 
second size (No. 2), they project for about 0‘24 mm., and are more numerous than the 
larger oxeas ; finally, forming the most superficial and most densely packed layer of 
spicules, follow the microxeas (No. 3), which do not project for more than 0'05 mm. 
The microxeas are also scattered through the choanosome, and are especially numerous 
about the surface of the larger canals, into the lumen of which they project. 
The spicules of the cortex are bound to^’ether by a fibrous collenchyma. 
The amphiasters are scattered generally throughout the sponge. They sometimes 
present an accessory whorl of actines around the middle of the axis, and then are 
suggestively similar to a “ Sceptrella.” The Scolopidae would thus appear to be nearly 
related to the Spirastrellidse. 
It is impossible, such is the impenetrability of the close palisade of cortical spicules, 
to obtain tangential sections, and thus one cannot determine the characters of the pores, 
neither can satisfactory radial sections be obtained by the paraffin method ; nothing but 
freezing can succeed in a case like this, and I leave this to subsequent observers. The 
mesoderm of the choanosome appears to be a granular collenchyma, an I the flagellated 
chambers are eurypylous. 
The general character of the spicular skeleton reminds one forcibly of that in 
Carter’s genus Trachya, and that of the cortex is distinctly Suberitic ; indeed, were 
the oxeas replaced by tylostyles, one would not hesitate to place the sponge with the 
Suberitidse. 
(ZOOL. CHALL. EXP. — PART LXIIl. — 1888.) 
Err 55 
