eee Royal Microscopical Society. 295 
other British marine invertebrata ; the locality from whence they 
were obtained is not yet known, except that they were taken at a 
depth of 540 fathoms. 
EXPLANATION OF PLATE LXVI. 
Fie. 1.—Dorvillia agariciformis, viewed laterally, enlarged $ diameter. 
2.—The same, as seen from above, nat. size. 
3.—Under surface of the upper portion or hood, showing where it becomes 
continuous with the basal part, the netted structure of the sarcode x 3 
linear. 
4.—A fragment of this netted portion, highly magnified, and showing the 
numerous minute irregularly stellate spicula interspersed through it. 
5.—Three of the minute irregularly stellate spicula x 500 linear. 
6.— One of the large bi-ternately terminating spicula, of which the greater 
portion of the skeleton is constructed, x 20 linear. 
7.—The same, viewed from above. 7a.—Portion of a simple porrecto- 
ternate spiculum from the same region, equally magnified. 
8.—One of the smooth anchorate spicula, abundant in the dependent root- 
lets and on the superior surface of the sponge, x 40 linear. 
9.—The anchorate termination of a variety. of the same. 
10.—Minute, rigid, delicately echinate hexradiate spicula, common in the 
sarcode of the sponge, x 100 linear. 
11.—An attenuate, flexuose, hexradiate spiculum, from the upper and super- 
ficial surface, x 50 linear. 
12.—The upper portion of an attenuate spinulate spiculum, from the same 
region, x 50 linear. 
13.—A simple attenuate, common on the superior and superficial layer, x 50 
linear. 
14.—Portion of an attenuate adpressly spined spiculum, similar to what 
obtains in the genus Pheronema.* 
15.—An attenuate linear spiculum, showing its tendency to develop into an 
hexradiate form, x 50 linear. 
16, 17.—Triradiate spicula, from the reticulated layer of sarcode shown at 
Fig. 3, x 100 linear. 
18.—A quadriradiate spiculum, from the same region, x 100 linear. 
19.—A minute clavate and profusely echinate spiculum, from the sarcode, 
x 100 linear. (This form is too scarce to be considered absolutely 
characteristic.) 
* This spiculum is probably an interloper, as may also eventually prove to 
be the case with the form represented at Fig. 11. The great depth at which this 
sponge was taken, and the nature of the mud with which it is associated, makes 
it reasonable to anticipate that Pheronema flourished in its vicinity. The spined 
Pec form of spiculum common to the last-named genus has also been 
etected. 
