1869.] DR. J.s. BOWERBANK ON SILICEO-FIBROUS SPONGES. 97 
elevated and margined, dispersed. Pores inconspicuous. Expansile 
dermal system—dermal membrane pellucid, furnished abundantly 
with small fusiformi-acerate spicula irregularly dispersed. Retentive 
spicula fusiformi-cylindrical, short and variable in size. Connecting 
spicula—apices discoid, irregularly cireular or oval, smooth and 
thin; margins entire; shafts short and conical. Skeleton—fibres 
cylindrical, smooth, their free terminations abundantly tuberculated ; 
tubercles cylindrical, short, terminations hemispherical. Interstitial 
membranes—tension-spicula fusiformi-acerate, short, rather nume- 
rous, dispersed. Gemmules membranous, spherical. 
Colour light fawn-brown in the dried state. 
Hab. Island of St. Vincent, West Indies (Rev. Lansdowne 
Guilding). 
Examined in the dried condition. 
This interesting little specimen is in the collection of the British 
Museum. It was obtained by the Rev. Lansdowne Guilding at the 
Island of St. Vincent, West Indies. 
The specimen is a small, unequally developed, cup-shaped sponge ; 
the margin is nearly oval, with an average diameter of seven-eighths 
of an inch, and it is about five-eighths of an inch high; the thick- 
ness of the sponge near the margin is about three lines. From its 
general aspect it would seem that the specimen was a young one in 
an early stage of development. The oscula are slightly elevated, 
have a thin margin, and are about one-third of a line in diameter ; 
they are equally distributed, and are about five or six lines apart, 
just as they might be expected to appear on a sponge of very much 
larger dimensions. 
The pores are dispersed on the outer surface of the cup; they are 
not readily detected even in a piece of the dermis when mounted in 
Canada balsam; they are found in intervals between the discoid 
plates, which frequently have semilunar notches to afford space for 
the passage of the inhalant streams. 
The dermal membrane is very translucent ; but the fusiformi- 
acerate spicula with which it is furnished are so exceedingly nume- 
rous that they render the discoid heads of the connecting spicula 
immediately beneath them perfectly undistinguishable. An average- 
sized one measured ;1, inch in length (Plate VI. fig. 12). The 
retentive spicula are comparatively few in number; they are very 
much smaller than the tension ones, and although mixed with them 
are readily distinguished by their fusiformi-cylindrical shape (Plate 
VI. figs. 13 & 14). 
The connecting spicula are singular in their form, and very cha- 
racteristic of the species; the normal form of their discoid heads 
appears to be nearly circular, but they vary to a very considerable 
extent to suit the circumstances of their situation. ‘Their margins 
lap over each other to frequently the extent of one-third or one-half 
of their diameters, so that they not only form a secure and con- 
tinuous platform for the support of the dermal membrane, but they 
also admit of a very considerable extent of lateral expansion and 
Proc. Zoo. Soc.—1869, No. VII. 
