301 
to our Knowledge of the Spongida. 
of delicate areolar sarcode charged with the spicules of the 
species. Spicules of two kinds, viz. :—1, skeleton-, acerate, 
long, curved, smooth, pointed gradually, l-40th by l-1800th 
inch in its greatest diameters (tig. 13); 2, flesh-spicule spini- 
spirulate, straight or curved irregularly, variable in length 
and thickness, the longest averaging 1-300th by 1-3000th 
inch in its gx-eatest diameters (tigs. 14 and 14 a). Spi¬ 
cules of both kinds equally mixed throughout the struc¬ 
ture. Lai'gest specimen about 1 inch square and of extreme 
thinness. 
Hah. Marine, on hard objects. 
Loc. Mauritius. 
Ohs. Examined in the di'ied state. There are several 
patches of this sponge, of various sizes under that mentioned, 
on fragments of old i*eef-coral which bear the name 11 Dr. 
Ayres,” in the late Dr. Bowei’bank’s collection; thi-ee of them 
are on that bearing the specimens of Chondrilla sacciformis , 
just described. Being loose and crumbling in its consist¬ 
ence, both when dry and after soaking in water, it fails to 
present the chondroid peculiarity of the Grumminida, while its 
Holorhaphidotc chai'acter and spiculation seem to claim for 
it a place in the family Suberitida. The spinispirulate flesh- 
spicule is a common form under various phases among the 
Suberitida; and one of the average largest specimens in 
Rhaphidhistia spectabilis , presenting ten lends , has been repi'e- 
sented under a highly magnified form, perhaps with a little 
more regularity than is natural, to show its elementary figure 
and composition (fig. 14 a). It is a strikingly beautiful 
object, separately or together, in Rhaphidhistia spectabilis 
when viewed under the mici’oscope, and hence the specific 
designation. When alluding to the different forms assumed 
by the spinispirula hereafter, it will be more particularly 
noticed. 
Hymeraphia spiniglohata. (PL XXVI. figs. 15, 16.) 
Laminiform, immeasurably thin, taking the form of the 
object over which it may be growing. Colour pellucid white. 
Texture loose. Surface even, echinated with long spicules. 
Pores, vents, and internal structure not recognizable in the 
dried state, from the extreme thinness of the layer. Spicules 
two kinds, viz. :—1, skeleton-,pinlike, straight, fusiform, shai-p- 
pointed gradually, l-43rd by 1-1500th inch in its greatest 
diameters ; head terminal, globular, a little larger in diameter 
than the shaft (PI. XXVI. fig. 15) ; 2, flesh-spicule, spini- 
globate or spiniglobospiral, the former about 1-857th inch in 
diameter (fig. 16, a , b, c, d). Skeleton-spicules projecting 
