174 



320x220^ in diameter; with hiuKlles of oxeas between the 

 lon^itiiclinal rows of fenestra;, and passing 2 to 4 mm. beyond 

 the outer surface, thus giving rise to a finely hirsute appearance 

 especially in the fossa; and valleys. 



Ectosomal spicules minute sigmaspires. 



Spicules.— Oxeds 2000 to 5000x12 to 30 /^, slender, often 

 undulating in outline, tapering to sharp points. 



Desma, generally with curved or semilunar epirhabd averag- 

 ing 400x30 /' and often bifurcate at the ends, smooth on the 

 concave edge, tuberculated and cladose on the convex surface, 

 one cladus in the middle of the convexity, often being of large 

 size and uniformly tuberculated ; again, the epirhabd may be 

 almost straight and uniformly tuberculated and cladose. 



Sigmaspire, 16.5 x 1.2 //, usually C-shaped, occasionally with an 

 extra coil, with rounded ends and with granular surface. (The 

 thickenings at the ends, shown in P'ig. le, disappear on 

 focussing carefully.) 



Locality : Durnford Pomt, Natal, bearing N.W. | W.,. 

 distant 12 miles ; depth, 90 fathoms ; bottom, broken shells. 



There are two specimens of this species, the dimensions in 

 centimetres beinii as f(^llows : — 



On the outer surface of the larger specimen is an ashen gray 

 patch of dead sponge 3 cm. in diameter and 3 mm. in thick- 

 ness. Several small holes on the suifaee lead to sand-lined 

 tubes, piobably of some worm. The desmas are thicker and 

 more tuberculated in the patch than elsewhere. 



The absence of ectosomal microstr(Migvles from this species 

 led me to suspect that the spicules of this kind occurring in 

 Scleritoderina llabdlifonuc SoUas and S. packanii Schmidt were 

 large sigmaspires, and a careful examination tended to confirm 

 this yiew. The microstrongvles of ^". fhihc'lllfoiuic are identical 

 with the sigmaspires in all respects except size, since they are 

 C shaped, occasionally with an extra coil, with rounded ends 

 and granular surface ; the resemblance in the case of S. packanii 

 is less obvious. The ectosomal rhabdi of Aciciilifcs, which are 

 curved and usually with granular ends, are also possibly de- 

 veloped from minute sigmaspires. 



