i74 



320 X 220 M in diameter ; with bundles of oxe.is between the 

 longitudinal rows of fenestra?, and passing 2 to 4 mm. beyond 

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

 especially in the fossne and valleys. 



Ectosomal spicules minute sigmaspires. 



spicules. — Oxeas 2000 to 5000 x 1 2 to 30 m, slender, often 

 undulating in outline, tapering to sharp points. 



Desma, generallv with ciu'ved or semilunar epirhabd averag- 

 ing 400 X 30 /' 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 Fig. ic, disappear on 

 focussing carefully. ) 



Locality : Durnford Pouit, Xatai, bearmg N.W. ^ W., 

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



There are two specimens of this species, the dimensions in 

 centimetres beinti as follows :- 



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 surface lead to sand-lined 

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

 more tuberculated in the patch than elsewhere. 



The absence of ectosomal microstrongyles from this species 

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

 Scleritodenua thihcUifoyiuc Sollas and S. pnckaidi Schmidt were 

 large sigmaspires, and a careful examination tended to confirm 

 this view. The microstrongyles of S. Jlnhfllifounc 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. packardi 

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

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

 veloped from minute sigmaspires. 



