378 
HYALONEMA (SKIANEMA) AEQUATORIALE. 
Foreign skeletal elements are always met in the deep-sea hexactinellids 
which have, like the specimen here described, been somewhat injured in capture. 
1 do not remember, however, ever having seen a sponge so rich in foreign spicules 
as this one. The spicules in question could be determined as foreign because 
they are identical with the pentac tines, pinules, hexasters, amphidiscs, etc., 
of Holascella euonyx, Hyalonema ( Hyalonema ) agassizi, Hyalonema ( Prionema ) 
fimbriatum, Hyalonema ( Phialonema ) pateriferum, and Hyalonema ( Prionema ) 
spinosum brought up in the same haul together with the sponge here under 
discussion. 
The dermal pinules (Plate 99 , figs. 29-31) are generally pentactine, rarely 
hexactine. The distal ray is straight, 200-260 /x long, and 5-8 /x thick at the 
base. It ends in a rather slender sharp-pointed terminal cone, and bears every- 
where, except at the base and at the tip, rather slender straight or slightly curved 
spines, which are all strongly inclined towards its tip. The maximum thickness 
of the distal ray, together with the spines, is 25-42 n . The lateral rays are 
cylindroconical, pointed, spiny, and 30-45 m long. The proximal ray of the rare 
hexactine forms (Plate 99 , fig. 29) is 9-42 n long. 
The gaslral pinules (Plate 99 , figs. 25-28, 36) are a little larger than the 
dermals and appear always to be pentactine. Their straight distal ray is 212- 
275 /x long, and 6-9 /x thick at the base. It ends with a long and slender sharp- 
pointed terminal cone and bears everywhere, except at the tip and at the base, 
remarkably sparse spines. These spines are long, slender, straight or slightly 
curved, and strongly inclined towards the tip of the ray. The maximum thick- 
ness of the distal ray, together with the spines, is 23-39 m- The lateral rays 
are 35-48 m long and, like those of the dermal pinules, cylindroconical and 
spined. 
The hypodermal and hypogastral pentactines seem to be quite similar. Their 
rays are conical, straight, and blunt. The proximal ray is generally 0.4-1 mm. 
long, and 16-50 m thick at the base. The lateral rays are 140-800 /x. 
The hexactine megascleres are mostly 360-850 /x in diameter, and have coni- 
cal, blunt, and straight rays 9-31 m thick at the base. A few fragments observed 
in the preparations indicate that some of these spicules attain a larger size. 
The ordinary superficial and choanosomal amphioxes are straight or slightly 
curved and usually more or less centrotyle. In some no trace of a central 
thickening could be made out. These spicules are 0.25 /x— 1-9 mm. long, and 
7-26 m thick near the middle. The central tyle is sometimes 6 m in transverse 
diameter, usually about 0.3 m more than the adjacent parts of the spicule. The 
