Knowledge of the Spongida. 321 
Loc. Van Diemen’s Land. 
Obs. Although this sponge, from its general appearance 
and spiculation, is closely allied to Phycopsis hirsuta, yet the 
form and greater length of the hirsute filaments, together with 
the less compact and generally much smaller axis, at least 
claim the separation above indicated. Like Phycopsts 
hirsuta it is closely allied to the genus Dictyocylindrus, Bk., 
but, for the same reason as that above assigned, it is placed 
among the Axinellida. The hirsute appendages are, of 
course, equivalent to the scopiform processes in Phakellia 
ventilabrum &ce. * 
We next come to two species of much more modified forms, 
although still fundamentally possessing the same kind of 
structure, and therefore giving rise to allied development. 
There are the same kind of echinated scopiform processes 
emanating from the same kind of condensed axial stem as in 
the other Axinellida, but the general form consists of long 
narrow branches which altogether present a feather-like group ; 
hence the genus will be termed “ Petlocaulis,” with the fol- 
lowing species :— 
x 
Prtilocaulis gracilis, n. gen. et sp. 
(Pl. XIII. fig. 8, and Pl. XIV. fig. 13.) 
Long, cylindrical, plumose branches, dichotomously and 
polychotomously divided, rising from a hard contracted solid 
base. Branches about half an inch in transverse diameter 
generally ; obtusely ended (Pl. XIII. fig. 8). Colour now, 
that is in the dried state, white, transparent. Axis consisting 
of slightly condensed fibre charged with the spicules of the 
species, from which emanate processes of the same structure 
in a floral form like the leaves of a Corinthian capital (fig. 8) ; 
passing through a delicate reticular tissue at the base and be- 
coming inflated, clavate, bifid, or irregularly divided at the 
extremities. Spicules of one form only, viz. acuate, curved 
chiefly towards the large end, smooth, sharp-pointed, about 
17 by 4-1800th inch in its greatest dimensions (Pl. XIV. 
fig. 13) ; more or less obscured in their echination, by being 
covered with an extension of the outer layer of the transparent 
fibre. Size of specimen, which consists of several branches in 
a group, 18 inches long by 93 inches in its greatest horizontal 
diameter. 
Hab. Marine. 
Loc. West Indies. 
Obs. This graceful specimen, looking in its dried state like 
a cluster of long, drooping, narrow, round feathers, affords 
