On a new Echinonematous Sponge. 
17 
II.— On Plectronella papillosa, a new Genus and Species of 
Echinonematous Sponqe. By W. J. Sollas, M.A., 
F.G.S., &c. 
[Plates IV.-VII.] 
Plectronella* papillosa (nov.). 
(Examined in the dried state.) 
Sponge (PL IV. figs. 1, 2) attached ; stem short, thick, irre¬ 
gular, dividing into a number of once- or twice-bifurcated 
branches; branches cylindro-conical, curving irregularly, 
uniting where grown in contact, consisting of a central axis 
and a number of conical papillae proceeding from it ; papillae 
£ inch long, inch in diameter, with simple, or bifid or trifid 
ends, arranged along the axis of the branch more or less spirally 
and at right angles to it, very numerous, producing the general 
outline of the sponge. Oscules and pores ? 
Colour drab or soft fawn-colour. 
Skeleton composed of three kinds of spicules :—(1) those of 
the interior; (2) those of the surface; (3) those of the 
sarcode. 
1. Spicules of the interior fusiform acerates, curved or 
straight, *00125 inch in diameter and 0*0225 inch long (PI. V. 
fig. 1), arranged in a confusedly fibrous manner, forming the 
chief skeleton of the sponge. Spicular fibres of the stem nu¬ 
merous, longitudinal, undulating, bifurcating and anastomosing, 
composed of acerate spicules lying longitudinally, frequently 
crossed by transverse ones, curving at intervals towards the 
exterior to supply a single fibre for the axial skeleton of each 
papilla (fig. 1, p. 18). Surface of the stem and papilhe echi- 
nat.ed by the forward projection of some of the acerate spicules. 
2. Spicules of the surface (PI. V. figs. 2, 21) triradiate; 
two rays smooth, abruptly pointed, equal in length, diverging 
at equal angles from the third, which is longer, spined, especi¬ 
ally towards the end, and terminated either by a sharp point 
or a rounded surface. Spines conical, usually bent backwards, 
talon-like. Length of the smooth rays, measured from the 
centre of the triradiate canal, 0*0028 inch, of spined ray 0*0055. 
Spicules arranged echinately, the pair of smooth rays seated 
on or immediately below the surface of the spicular fibre; 
the spined ray projecting obliquely forwards. 
3. Flesh-spicules extremely fine filaments, 0*005 inch long, 
straight, or curved once, twice, or three times (PI. V. figs. 3, 4); 
* nXf/KTpnv, a spur. 
Ann. & Mag. N. Hist. Ser. 5. Vol. iii. 
2 
