72 
THE VOYAGE OF H.M.S. CHALLENGER. 
also defend the upper and lower margins of the poriferous areas; the upper fringe is directed 
downwards over the area and over the lower fringe ; this also is directed downwards and 
therefore away from the area. The skin of the sponge is produced about the proximal 
part of the fringes, both of the oscule and poriferous areas, thus converting them into 
membranous tubes. 
The rootlets are small, without basal cones, for the most part torn away. 
In young forms the sponge resembles Thenea grayi in form, the oscule is lateral and 
a single poriferous area is situated on the opposite side ; additional poriferous areas 
appear to be added with growth. 
Spicules. — I. Megascleres. 1. Oxea, fusiform, 5’0 by 0‘06, and 9’3 by 0‘05 mm. 
2. Protriaene of the usual form, with long conical cladi curving forwards ; rhabdome 
3 '9 by 0’052 mm.; cladi 0’785 by 0‘04 mm.; chord 1*4 mm. 
3. DicTiotrisene of the usual form; rhabdome 3T4 by 0’03 to O' 05 mm.; protocladi 
0T63 by 0‘04 to 0'045 mm.; deuterocladi 0'678 by 0’032 mm, 
4. Somal and radical anatrisenes (PI. VIII. figs. 2, 3) of the same form. A slender 
cylindrical rhabdome with slender, sharply-pointed, much recurved, cladi ; in specimens 
from Station 106 the rhabdome is frequently produced beyond the cladal origin for a 
variable distance, so as to give rise to a mere mucrone or tubercle, or a long rod-like spine, 
either rounded off or sharply pointed at the end ; in other words the cladome is sub- 
terminal to mesactinal in position. Ehabdome 4'641 to 5‘56 (probably often longer) by 
0'0125 mm.; cladi 0’4 by 0'0115 mm.; chord 0'239 mm,; distal prolongation of the 
rhabdome from O'O to 0'357 mm. long. 
II. Microscleres. 5. Plesiaster (PI, VIII. figs. 4-5) small, with slender actines 
obviously spiral, seldom monocentral ; actines often minutely spined ; a single actine 
0‘06 to 0'09 by 0‘0039 mm. 
6. Spiraster (PI. VIII. figs. 7, 8) large, a spire with numerous spirally arranged 
spines, sometimes roughened, and sometimes slightly tylote ; total length from 0'0395 
to 0'0474, length of a single spine 0'0012 to 0‘0019 mm. 
Metaster ; absent. 
Colour. — Yellowish- white (Station 123) ; greyish-white (Station 106). 
Habitat. — Station 106, south-west of Sierra Leone, August 25, 1873 ; lat. 1° 47' N., 
long. 24° 26' W.; depth, 1850 fathoms; bottom, Globigerina ooze; bottom temperature, 
36°-6. 
Station 123, off Macio, September 11, 1873; lat. 10° 9' S,, long. 35° 11' W.; depth, 
1715 fathoms; bottom, red mud; bottom temperature, 37°. 
Specimens described by Oscar Schmidt were obtained from Bequia at 1507 and 
1591 fathoms ; and from lat. 24° 36' N., long. 80° 5' W., at 955 fathoms. 
Remarks. — In giving an account of Thenea muricata, Bwk., I suggested that 
