340 Mr. R. Hope on two new 
at each end; measuring on the average about *188 x ‘005 
millim. (fig. B, 3). 
Microsclera (?).—There are present in places, chiefly near 
the surface of the sponge, a few long and exceedingly fine 
styles, sometimes microspined at the base. They are very 
few and appear to be local in their distribution in the sponge 
and wanting altogether in many parts of it; probably they 
are to be looked upon rather as varieties or immature forms 
of the megasclera. 
From what has been stated it will be seen that this sponge 
agrees with the species of the genus Trachytedania in the 
possession of a skeleton composed mainly of spined styles and 
smooth tylota; that genus also already comprises as one of 
its two species a thin incrusting sponge, 7. spinata (P. Z. S. 
1881, p. 122), with a skeletal structure of the kind which is 
frequently present, with some comparatively slight modifica- 
tions, in sponges of that habit, and closely similar to that of 
the sponge under consideration. There is, however, no echi- 
nating spicule in 7. spinata, and it is by the possession of a 
special spicule of this nature, the straight, entirely spined 
styles, that Z.(?) echinata differs most markedly from the 
other two species of the genus. 
In some groups of the family Desmacidonide, R. & D., 
this seems to be a feature of minor importance (see ‘ Chal- 
lenger’ Monaxonida, p. 129, and supra, p. 337) ; whether it 
is so also in this case, the data afforded by so small a series of 
forms appear to me insufficient to base a decision on them. 
The absence of trichites would present another point of diver- 
gence from the diagnosis of the family Tedaniine, R. & D. 
(‘ Challenger’ Monaxonida, p. 50), if the few long and fine 
spicules which are present here be, as seems most likely, 
merely modifications of the megasclera; this difference, how- 
ever, seems of less importance, as the same doubt as to the 
nature of the ‘‘rhaphides” in the closely allied. genus Ze- 
dania is expressed by Messrs. Ridley and Dendy (‘ Chal- 
lenger’ Monaxonida, p. 56); the oxeote spicules, smooth or 
microspined, which are present in some of the species of 
Tedania and which are noted in Dr. Gray’s original diag- 
nosis (P. Z. 8. 1867, p. 520), are absent both in this sponge 
and in the other species of Zrachytedania, the fine spicules in 
the latter, whatever their nature, being respectively stylote 
(P. Z. 8S. 1881, 2. ¢.) and “ oxeote slightly thicker at one end 
than the other’’ (‘ Challenger? Monaxonida, p. 57). It may 
be remarked that what may perhaps be homologous spicules 
abound in some species of the Clavuline (e. g. Suderites 
