EEPOET ON THE TETRACTINELLIDA. 
249 
chrote 0'08 to 0'118 mm. in thickness (composed of vesicular tissue, containing beneath 
the epithelium a single layer of minute chiasters) of the sterrastral layer, and an inner 
fibrous layer 0'16 to 0‘238 mm. in thickness. Pores in sieves hispidated by cortical 
oxeas, leading into incurrent chones. Oscules as in Geodia harretti, Bowerbank, 
margins hispidated by cortical oxeas. 
Spicules. — I. Megascleres. 1. Somal oxea, 2'84 by 0'044 mm. (B. M.), and from 3'18 
by 0’0473 to 3‘51 by 0'0276 mm. 2. Cortical oxea, 0’39 by 0‘008 mm. Z.Orthotrisene, 
rhabdome 276 by 0’07 mm. (B. M.), and 3'57 by 0'0513 mm., cladus 0‘254 mm. long. 
4. Anatrisene, rhabdome 4‘82 by 0’019 mm. (B. M.), and 6'36 by 0'0197 mm., cladome 
variable, cladi sometimes extending outwards at right angles from the rhabdome for 
nearly half their length before recurving backwards, sometimes extending outwards and 
backwards from their origin ; an example of the latter gave the following measurements — 
cladus 0’063 mm. long, chord 0’09 mm., sagitta 0’059 mm. ; one of the former, cladus 
0'0315 mm. long, chord 0'0513 mm., sagitta 0‘0479 mm., and another, cladus 0'0316 mm. 
for the horizontal part of its course, 0'0434 for its backwardly directed terminal part, 
chord 0‘083 mm., sagitta 0'0474 mm. 
II. Microscleres. 5. Sterraster, 0’071 mm. in diameter (B. M.) and 0‘067 mm. 6. 
Somal chiaster, actines short, cylindrical, truncated at the ends, O’Ol mm. in diameter. 
7. Choanosomal chiaster, 0*0237 mm. in diameter. 
Colour. — Cream-yellow in the dried state. 
Habitat. — Quarnero, Adriatic. 
Remarks. — The measurements marked (B. M.) were obtained from a type-slide in the 
British Museum collection, the others from a large fragment presented me by Professor 
von Graff. They do not accord very closely, but this is possibly due to the spicules 
having been obtained from sponges of different size. In its general characters the 
sponge resembles Geodia harretti, Bowerbank. I received two specimens of Schmidt’s 
type from Professor von Graff ; in one of them the cortex is only 1 mm. thick and 
abundantly furnished with chones, but not traversed by the megascleres or only rarely 
so, while in the other the cortex is 3 mm. thick, and hispidated by oxeas and anatrisenes, 
which pass in great numbers through its substance, and project nearly 2 mm. beyond the 
surface ; no chones are present in the cortex of this specimen, except those of the oscules, 
which occur in a shallow depressed area, formed of modified cortex. 
Geodia tumulosa, Bowerbank. 
Geodia tumulosa, Bowerbank, Proc. Zool. Soc. Bond., p. 628, pi. xlvii., 1872. 
Geodia gihherosa, Lamarck, Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 362, 1882. 
Sponge. — Massive, sessile, tumulose. Oscular areas situated on the ends of the tumu- 
lous projections; surface minutely hispidated. Cortex, 1*43 mm. in thickness, con- 
(ZOOL. CHALL. EXP. — PART LXIII. — 1887.) Err 32 
