218 Mr. W. S. Kent on two new Siliceous Sponges. 
size, in point of structure are deserving of an equal and per- 
haps even a greater amount of attention. 
The first of these which I shall proceed to describe would 
seem, in the present transitional condition of the classification 
of the Porifera, to find its most natural position among tha 
wed of the Silicea known as the order ARMATOSPONGLE of 
E. Gray, and of which the genera Tethya, Microciona, 
and Esperia are familiar representatives. 
All the examples of this form taken were, without excep- 
"wt attached to specimens of the compound Madrepore Lopho- 
a prolifera or its variety anthophyllites*. The external 
seis natural size, of a specimen attached to the coral is in- 
dicated at Pl. X . fig.1; fig. 2 being a transverse section of 
another specimen magnified about two diameters, while fig. 3 
represents a small fragment with two dividing fascicles of 
spicula which form the upright supporting pillars to the *pin- 
cushion-like" cortex. The mh ty entirely siliceous, which 
enter into the skeletal structure of this sponge may be referred 
to three distinct types. 
1. Simple acerate spicula of two s 
a. Very minute and attenuate, es papas gig inch in 
len XV. figs. 4 & 4a 
b. e the same type, but comparatively blunt-pointed, 
eraging a length of 44. a5 inch. Pl. XV. fig. 5. 
2. [AP Ced or “ spinulate" spicula; heads or bases usu- 
nd pom Eres slightly depressed; average 
y 
length 4 . Pl. XV. figs. 6 a, 
3. À minute form, most closely approaching the “ palmated 
inequianchorate” type owerbank, Brit. g 
pl. 6. fig. 138, spicule of an undescribed sponge) ; 
varying in length from 4455 to 4i, inch. PI. XV. 
fig. 7. 
In the first pe we nd a thin basal layer of sarcode 
covering the object to which the sponge is attached, and m 
which. are dutGbufed fascicles of the minuter acerate spicules, 
with a few isolated larger ones of the same type interspersed. 
From this layer there proceed at right angles upright shafts 
or pillars composed entirely of these larger acerate spicula, 
attenuate at their base, but expanding and evincing a ten- 
* I entirely agree with Dr. P. M. Duncan that these two forms are 
simply variations of the same species 
