295 
to our Knowledge of the Spongida. 
(fig. 10, c) ; no. 2 (fig. 10, h) chiefly forms the fibre ; and 
no. 3 is the echinating spicule, plentifully distributed about 
the latter (fig. 10, d). Size of entire specimen about 1 inch, 
and the branches about 3-24ths inch in diameter respectively. 
Hah. Marine. 
Loc. West coast of Africa. 
Ohs. Examined in the dried state. This sponge, numbered 
as above mentioned, may be found in a little pill-box in the 
British Museum, and was presented by the Rev. Mr. Allen. 
To render it more easily recognizable, it bears on its surface 
the remains of a parasitic polype ( Palythoa ). Its spiculation 
is very much like that of Trikentrion muricatum , but has, in 
addition, the setaceous acuate very common among this kind 
of sponges, although absent in T. muricatum. When, how¬ 
ever, the general form and internal structure of T. leave is 
compared with T. muricatum , there is a still greater difference; 
for while the surface of the latter is covered Avith little conical 
processes of the sponge-substance (another common feature of 
many of the Echinonemata, particularly well-shown in Esper’s 
and Mr. Sollas’s representations of this sponge respectively), 
that of T. leave is even and setaceous, more like that of a 
Dictyocylindrus or Axinella : Sdt.; again, while the structure 
generally of T. leave is composed of loose or compressible, 
reticulated fibre, that of T. muricatum is just the opposite, 
viz. hard, dense, and compact, becoming still more so towards 
the axis of the branch—another character almost peculiar to 
many of the Echinonemata. These, together with other dif¬ 
ferences, viz. in size, colour, and general form, are ample for 
making T. leave a distinct species ; but it is remarkable that 
both this and T. muricatum should come from the west coast 
of Africa, and that, as yet, they should not have been shown 
to have come from any other part of the world, even going so 
far back as Pallas in 1756. 
Dictyocylindrus, Bk. 
Order ii. Silicea, Suborder i., Genus 10 (pp. 3, 6, 
op. et loc. cif.). 
Allied to the genus Trikentrion , and typical of one of the 
groups into which the Pluriformia will hereafter have to be 
divided, is Dr. Bowerbank’s genus Dictyocylindrus , which, so 
far as his diagnosis goes (op. cit. p. 6), is well defined, but 
would have been better if the echinating spicule, although 
very sparse in many species, had been mentioned, as this at 
once would have placed it in my order Echinonemata, under 
the family Ectyonida. My object, however, in introducing 
20 * 
