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 /u throughout or slightly centrotyle. It bears very 

 low and broad, tubercle-like, scattered protuberances (spines). The terminal 

 anchors are 12-18 ^ long, a fifth to a fourth of the whole spicule, and 19-25 m 

 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 /x long, most 

 frequently about 18.3 n. The shaft is straight or slightly curved, generally 

 of a fairly uniform thickness of 0.7-1.2 n throughout, and covered with minute 

 scattered spines. The terminal anchors are 3.5-8 ^ long, a quarter to a third 

 of the whole spicule, and 4.5-8 ^ 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 (Skianemn) umbra- 

 culuvi 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 l)y the possession of spheres. 



Hyalonema (Skianema) umbraculum, sp. nov. 

 Plate 101, figs. 4-17; Plate 102, figs. 1-8; Plate 103, figs. 1-3G. 



Two fragmentary specimens of this species were trawled in the Central 

 Tropical Pacific at Station 4740 on 11 February, 1905; 9° 2.1' 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 aljout 



