154 
THE VOYAGE OF H.M.S. CHALLENGEE. 
Trihrachium schmidtii, Weltner (Pi. XVII. ; PI. XLI. fig. 5). 
TrihracMon schmidtii, Weltner, Beitrage zur Kenntniss der Spongien., Tnaug. Diss. Freiburg, 
pp. 50-55, Taf. L fig. 8 ; Taf. iii. figs. 29-41, 43, 1882. 
Sponge (PI. XVII. fig. 1), somewhat bulb-shaped ; consisting of a spherical body and 
a long, tapering, cylindrical, cloacal tube. In addition to a single terminal oscule opening 
at the end of the cloacal tube by a sphinctrate aperture, oscular pore-sieves occur generally 
distributed over the sides of the cloacal tube. Pores small, single, distributed in inter- 
cladal areas of the epithelium of the sponge body. Ectosome a cortex. 
Spicules. — I. Megascleres. 1. Oxea (PI. XVII. fig. 2), fusiform, with sharply pointed 
ends, 4*9 by 0’0671 mm. ; the average length is 4'3 mm. 
2. Somal orthotrisene (PI. XVII. fig. 3), rhabdome attenuating to a very finely 
pointed extremity ; cladi conical, sharply pointed or strongylate, diverging at first 
outwards and forwards, and either gradually curving into horizontality or becoming 
suddenly bent in the middle of their course ; usually bent in the middle in a horizontal 
plane, or more or less crooked, sometimes one or more cladi are bifurcate ; seldom of 
equal length in the same cladome. Rhabdome 4'3 to 4‘9 by 0’087 to 0‘095 mm. ; 
cladi of very various dimensions, maximum length 0‘475 mm. 
3. Cloacal orthodisene (PI. XVII. fig. 7). This is a reduced orthotrisene; the rbab- 
dome is cylindrical or slightly fusiform, tapering to a sharp point ; the cladi diverge out- 
wards and forwards for a very short distance, and then wholly outwards. They are 
conical, sharply pointed and frequently more or less crooked. The forward direction of 
the cladi near their origin is shown by the course of the contained axial fibres, but not 
otherwise indicated except by a concavity lying between them in the middle of the front 
of the cladome. Rhabdome 3 “9 by 0‘043 mm. at the origin of cladome, increasing towards 
the rhabdal origin to 0“0592 mm.; cladi 0‘65 by 0*043 mm. 
4. Anatrisene, often reduced to an anadisene and anamonsene (PL XVII. figs. 4-6) ; 
rhabdome conical, attenuating to an almost filiform extremity ; cladi variable, usually 
extending more outwards than backwards, sharply pointed or strongylate. Rhabdome 
1*35 by 0*01 mm., cladi 0*0197 to 0*0236 mm. in length, cladus of an anamonsene 0*0355 
mm. in length. 
II. Microscleres. 5. Sanidaster (PL XVII. fig. 8), rhabdome straight and slender ; 
cladi numerous, short, with rounded ends ; total length 0*012 mm., total width 0*004 
mm., rhabdome about 0*001 mm. in diameter. 
6. Oxyaster. This spicule would appear to be characteristically absent, but a single 
example, 0*0156 mm. in diameter, was observed in a scleroblastic cell, 0*0185 mm. in 
diameter. 
Colour. — Y ello wish-white. 
Habitat. — Bahia; shallow water, 7 to 20 fathoms; September 1873. Weltner’s 
