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THE YOYAGE OF H.M.S. CHALLENGER. 
those of larger forms, e.g., the sterrasters of Cydonium hirsutus. The ends of the actines 
are not produced into spines, but rounded and covered with granulations. 
Synops vosmaeri, Sol] as (PI. XXIII. ). 
Synops vosmaeri, Sollas, Prelim. Account, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 197, 1886. 
Sponge (PI. XXIII. fig. 1). — Cylindrical, with a cup-shaped depression, surrounded by 
a rounded margin, at the upper end ; erect, attached. Oscules confined to the cup-shaped 
"depression, the patent openings of excurrent chones. Pores in sieves (PI. XXIII. 
fig. 17), collected into oval depressed areas on the lateral surface, which is raised into 
irregular rounded ridges running chiefly longitudinally, the depressions bearing the pores 
lying between. Some of the depressions are continued as tubes into the middle of the 
sponge-body, their walls being lined by an extension of the cortex, much reduced in 
thickness, and bearing numerous pore-sieves. Cortex ; the ectochrote is crowded with 
spherasters of the same kind as those associated with the e23ithelium ; the sterrastral layer 
is thin and the fibrous layer underlying it remarkably thick. 
Spicules. — I. Megascleres. 1. Somal oxea (PI. XXIII. figs. 3, 4, 12), fusiform, 
sharpl}^ pointed or not, straight or curved, from 1'321 by 0'016 to 1’68 by 0'008 mm. 
2. Cortical oxea (PL XXIII. figs. 6, 14), slender, fusiform, 0’3 by 0‘004 mm. 
3. Ortliotrisene (PI. XXIII. fig. 5), rhabdome conical, usually sharply pointed ; cladi 
simple, diverging outwards, at first slightly forwards, and subsequently backwards. 
Ehabdome 1‘107 by 0‘0387 mm., cladi 0*286 mm. long. 
II. Microscleres. 4. Sterraster (PI. XXIII. figs. 7, 9), small, spherical, ends of the 
actines slightly smaller than those of the corresponding spicule of Synops nitidus, not so 
closely contiguous, and with fewer spinelets ; 0*0394 mm. in diameter. 
5. Somal spheraster (PI. XXIII. fig. 11), minute, a somewhat small centrum; short, 
relatively thick, minute actines, truncate or rounded at the ends ; 0*004 mm. in diameter. 
6. Choanosomal oxyaster (PI. XXIII. figs. 8, 10), a scarcely perceptible centrum, 
long, slender, hair-like actines, not numerous, usually six to ten in number ; length of a 
single actine 0*0118 ; total diameter 0*0256 mm. In the neighbourhood of the subcortical 
canals this form becomes somewhat modified, the actines are shorter and more numerous, 
and a small but evident centrum is present ; the diameter of the variety is about 
0*016 mm. 
Colour. — Cream-white, stained pink in places by a rhodophycaceous Alga. 
Habitat. — Station 122, off Barra Grande, September 10, 1873; lat. 9° 5' S., long. 
34° 50' W. ; depth, 350 fathoms ; bottom, red mud. Trawled. 
Remarks. — The single specimen of this sponge is fairly symmetrical in shape, and 
perfect from base to summit ; it measures 96 mm. in height and 50 mm. in diameter. The 
margin of the cup at the summit is thicker and higher on one side than the other. 
