HYALONEMA (SKIANEMA) UMBRACULUM. 
383 
frequently about 69.5 n. The shaft is straight or slightly curved, and of a 
uniform thickness of 2.5-5 n throughout or slightly centrotyle. It bears very 
low and broad, tubercle-like, scattered protuberances (spines). The terminal 
anchors are 12-18 n long, a fifth to a fourth of the whole spicule, and 19-25 p 
broad. The proportion of the length to the breadth of the anchors is 100 to 
134-167, on an average 100 : 148.1. Each terminal anchor consists of from 
twelve to sixteen teeth. The individual teeth are curved only slightly in their 
proximal and distal parts, but rather strongly in their middle-part. Their total 
curvature is such that their nearly straight ends diverge. The anchor-teeth are 
rather slender and pointed at the end. 
The small micramphidiscs (Plate 99, figs. 21-24) are 14-25.5 n long, most 
frequently about 18.3 p. The shaft is straight or slightly curved, generally 
of a fairly uniform thickness of 0.7-1. 2 p throughout, and covered with minute 
scattered spines. The terminal anchors are 3.5-8 m long, a quarter to a third 
of the whole spicule, and 4.5-8 n broad. The proportion of the length to the 
breadth of the anchors is 100 to 81-143, on an average 100 : 98. The individual 
teeth are rather strongly and uniformly curved in their proximal part, and nearly 
straight in their distal part. The straight distal parts of the teeth of the same 
anchor are more or less parallel. 
The nearest allies of the above sponge are Hyalonema' {Skianema) umbra- 
culum and H. ( Thallonema ) geminatum. From H. (S ) . umbraculum it differs 
by having smaller large micramphidiscs, from H. ( T .) geminatum by being desti- 
tute of the geminate amphidiscs and the different shape of the pinules, and from 
both by the possession of spheres. 
Hyalonema (Skianema) umbraculum, sp. nov. 
Plate 101, figs. 4-17; Plate 102, figs. 1-8; Plate 103, figs. 1-36. 
Two fragmentary specimens of this species were trawled in the Central 
Tropical Pacific at Station 4740 on 11 February, 1905; 9° 2.P S., 123° 20.1' W. ; 
depth 4429 m. (2422 f.); they grew on a bottom of dark gray Globigerina 
ooze; the bottom-temperature was 34.2°. 
The terminal anchors of the large macramphidiscs are very broad and 
low, umbrella-shaped. To this the name refers. 
Shape and size. The larger specimen is an irregular oval lamella with 
lacerated margin, from one of the narrow ends of which a couple of stout stalk- 
spicules protrude. The lamella is 62 mm. long, 39 mm. broad, and about 
