38 
THE VOYAGE OF H.M.S. CHALLENGEE. 
21 mm. in diameter. The smaller specimen differs in other details from the larger; there 
is but one oscule, and the oscular conules are not so much longer than those of the general 
surface as they are on the larger specimen ; the colour is almost snow-white, while the 
larger one is tinted faintly brown. These external differences are accompanied by a 
difference in the length but not in the thickness of the spicules, those of the smaller 
specimen being the shorter. It occurred to me that these differences might possibly be 
sexual, and thin slices from both specimens were therefore particularly examined for 
sexual elements ; in neither, however, do they exist. 
The cortex presents the typical Crcmiella structure ; the outer layer is from 0‘32 to 
l‘G mm. thick, the inner layer 1'43 to 1’93 mm. thick, and the total thickness is from 
1*75 to 2‘4 mm. 
The flagellated chambers measure about 0’0276 and 0’037 mm. along two diameters, 
the prosodal canals are short, not over O’OIG mm. long, the aphodal canals are longer; 
the choanocytes are about 0'0039 mm. in diameter and 0‘0039 mm. long, where the 
flagellum is not extended; where it is, they are 0'006 mm. long, and the flagellum over 
0‘01 mm. long. 
Craniella schmidtii, n. sp. 
Sponge spherical, similar to Craniella cranium. 
Spicules. — I. Megascleres. 1. Somal oxea, fusiform, the proximal end more sharply 
pointed than the distal, but not filiform; 1'34 by 0'03 mm. to 1’6 by 0‘04 mm. 
2. Cortical oxea fusiform, 0‘414 mm. by 0’0276 mm. 
3. Protrisene, of this there are two varieties which pass into each other; one with 
shorter and stouter, the other with longer and more slender cladi; in the latter the rhab- 
dome has a diameter of 0'0118 mm., and the cladi measure from 0'142 by 0’012 mm. to 
0’16 byO'016 mm., in the former the diameter of the rhabdome is 0‘0237 mm., and the 
cladi measure 0'127 by 0‘0237 mm. 
4. Anatrisene, a rapidly tapering rhabdome, with the cladi extending horizontally 
for a great part of their course before recurving. Cladi 0'075 by 0 '0158 mm., chord 
0‘01 mm.; the axial fibre of the rhabdome extends 0‘0158 mm. beyond the origin 
of the cladi. 
II. Microsclere. 5. Sigmaspires numerous, 0‘0197 mm. long. 
Colour. — Greyish-white. 
Habitat. — Station 24, off Culebra Island, West Indies, March 25, 1873; lat. 
18° 38' 30" N., long. 65° 5' 30" W.; depth, 390 fathoms ; bottom, Pteropod ooze. 
Remarks. — This little sponge, 4*5 mm. in diameter, resembles in outward appearance 
and general structure Craniella cranium, Miill., of which I have given a full account in my 
