349 
to our Knowledge of the Spongida. 
ton- and two flesh-spicules), to which must be added the foreign 
material, viz. the quartz grains:—1, skeleton-spicule, acerate, 
long, smooth, curved, sharp-pointed gradually, l-22nd by 
1-lSOOth inch in its greatest dimensions (fig. 11); 2, flesh- 
spicule, stelliform, very minute and delicate, composed more 
or less of eight rays, radiating from the centre direct (that is, 
without inflation there), l-2000th inch in diameter (fig. 12,a, b) ; 
3, flesh-spicule, bacilliform, straight, cylindrical, obtuse at the 
ends, spined all over, about 1-666th by 1-6000th inch in its 
greatest dimensions (fig. 13, a, b ) ; 4, quartz grains, variable 
in size, about the diameter of the flesh-spicules (fig. 14). 
No. 1 is confined to the interior, mixed with a few of the flesh- 
spicules ; nos. 2 and 3, together with the quartz grains and a 
few fine acerates, are more abundant in the cortex. Size of 
specimen 1^ inch high by 1^ inch in transverse diameter about 
the middle, and 1 inch at the base. 
Hah . Marine, on hard objects. 
Loc. Port Adelaide, Australia {Cuming). 
Obs. Examined in the dried state and after soaking in 
water. This specimen is in the British Museum, and bears 
the register no. 55. 3. 14. 8, with my running no. E, 301 h , 
18. It has grown upon the outside of the flat valve of a large 
Pecten , where, at first, it looks very much like a specimen of 
Halichondria ficus , Johnst. On examining it, however, more 
attentively and after soaking, it is found to have a fleshy 
cortex not unlike that of the Gumminida in consistence; in 
form and structure it is like Geodia , and its internal spicula- 
tion is like that of both Geodia and Stelletta so far as the acerate 
spicule goes; but there is no trifid spicule, and no zonular 
arrangement, of course, at the circumference. With all these 
characters it is impossible to assign it to either; and therefore 
a new genus has been made for it under the name of Stelletti- 
nog>sis , after Stelletta , whose spiculation generally, minus the 
trifid forms, its spiculation so nearly resembles that at first 
sight there appears to be no difference. Ifs place should, 
perhaps, be in the order Plolorhaphidota, among or after the 
Suberitida, and before the Pachytragida. 
Stellettinopsis simplex , n. sp. 
(PI. XXVIII. figs. 16-18.) 
Massive, convex, lobate, sessile. Colour tawny brown. 
Texture loose. Surface firm, even, irregularly undulating, 
without cortex. Pores not seen. Vents grouped in a depres¬ 
sion on the lower aspect. Internal structure confused, con¬ 
sisting of open areolar sarcode, crumb-of-bread-like, charged 
with spicules of the species, and traversed by the excretory 
