832 
DE. J. S. BOWEEBANK ON THE ANATOMY 
other in length and in the width of the prongs of the fork apart, but they all haye 
them unequal in length. It is probably an auxiliary skeleton and external defensive 
spiculum. 
Elongo-eecuevate dentato-bieotulate (Plate XXXVI. fig. 20). — From Eyalonema 
mirahilis, Geay. This spiculum is from the same sponge as that represented by fig. 4, 
Plate XXXI. Part II. It is an extreme variety of that form. Fig. 7, a, in the same 
plate, appears to be an intermediate variety. 
Elongo-eecuevate dentato-bieotijlate (Plate XXXVI. fig. 21). — From soundings 
in the Indian Ocean, 2200 fathoms. The smooth shaft and the widely-spread teeth of 
this spiculum render it very probable that it belongs to an unknown species of Hyalo- 
nema. 
Recuevo-acutely dentate bieotulate (Plate XXXVI. fig. 22). — From soundings in 
the Indian Ocean, 2200 fathoms. The thin smooth shaft and the acutely-terminated 
teeth of this form indicate probably a species of Hyalonema unknown to naturalists at 
present. 
Recuevo-dentato-bieotulate (Plate XXXVI. fig. 23). — From soundings in the 
Indian Ocean, 2200 fathoms. The fragment represented is most probably from 
another unknown species of Hyalonema. It is the only specimen of this form that 
has, I believe, been found. 
Attenuato-cylindeical, veeticillately seined (Plate XXXVI. figs. 24 & 25). — 
These spicula are found dispersed in abundance on the interstitial and dermal mem- 
branes of HymerapMa verticillata^ Boweebane, MS. A new British species, brought 
up by the sounding-line from 100 fathoms, off the Western Coast of Ireland, by the 
officers of H.M. ship ‘ Porcupine.’ It is remarkable as being the only verticillately- 
spined spiculum that has been found in a British species of sponge, and also for 
exhibiting the mode of development of that class of spicula. In the earliest stage the 
spiculum is long, slender, and perfectly smooth ; as the growth proceeds, two or three 
shght inflations appear near the middle of the shaft, and others are successively deve- 
loped beyond them, until the spiculum assumes the moniliform appearance represented 
by fig. 25. As the inflations increase in number and size, a few incipient spines appear 
in a circumferential line at their greatest diameter ; and as the growth proceeds, the 
spines increase in number and size, and the spaces between the inflations are filled up by 
the expansion of the shaft ; and this mode of development is continued until the adult 
spiculum assumes the form represented by fig. 24. This form appears to act both as a 
tension and a defensive spiculum. 
Spicula of the Sarcode. 
Toequeato-bidentate iNEQUi-ANCHOEATE (Plate XXXVI. fig. 26). — From an unde- 
scribed species of sponge. Freeman tie. Western Australia, Sent to me, mounted in 
Canada balsam, by Mr. Geoege Clifton. This is closely allied to the one represented 
by fig. 12, Plate XXXL Part II. 
