424 
THE VOYAGE OF H.M.S. CHALLENGER. 
Both inner and outer surface rendered thinly hispid by slender projecting oxeate 
spicules, which extend further from the surface in the lower and interior part of the vase 
than elsewhere. 
Ectosome, thin, coUenchymatous. Choanosome, mesoderm a coUenchyma, flagellated 
chambers eurypylous, about 0’0275 to 0'0395 mm. in diameter, often oval in section, 
then, 0‘0434 by 0'0353 mm. in diameter. 
Spicules. — I. Megascleres. 1. Axial oxea (PI. X. fig. 3), stout, fusiform, obtusely 
pointed, straight or curved ; 3 '034 by 0'0774 mm. 
2. Hispidating oxea (PI. X. fig. 2), slender, cylindrical, sharply pointed, 3 '927 by 
0'0387 mm. 
II. Microscleres. 3. Aster, with few actines (PI. X. fig. 6), centrum absent, actines 
variable in number, most frequently four, then usually of calthrops form, sometimes less, 
three or two, then producing a centrotylote microxea, or only one ; sometimes more, as 
many as five or six. The inclination of the actines is also variable, sometimes a tetrac- 
tinose form is not a microcalthrops but a staurus, and a triactiiiose form may resemble a 
staurus with one actine suppressed. The variations in the form of this spicule are similar 
to those of the corresponding spicule in Thenea. The actines are conical, strongylate, and 
slightly roughened towards the ends ; they measure 0'0276 by 0'004 mm. 
4. Asters, with several actines. These differ from the preceding in presenting 
slightly smaller dimensions and somewhat more numerous actines, usually six to eight in 
number. Length of a single actine, 0’008 mm. 
Colour . — White, of a faint grejfish tinge. 
Habitat . — Station 192, September 26, 1874 ; lat. 5° 49' 15" S., long. 132° 14' 15" 
E. ; depth, 140 fathoms ; bottom, blue mud. Trawled. 
Remarks . — Only a single specimen of this elegant vase-shaped sponge was trawled. 
It measures 73 by 51 mm. across the brim ; its total height is 46 mm. ; the thickness of 
the wall about 3 mm. ; the rigid stem is 12 mm. high and 6 mm. thick. 
The interdigitating excurrent and incurrent canals cross the wall transversely, so that 
in transverse section the choanosome appears more or less regularly folded (PI. X. fig. 10). 
Branches looking like minor folds proceed from both sets of canals, which subdivide till 
only a single layer of flagellated chambers intervenes between their ultimate ramifications. 
The ectosome, averaging about 0'318 mm. in thickness, is a coUenchymatous layer 
coated by epithelium, which on the incurrent face is subdivided into an outer layer which 
is perforated by the pores, and which forms the roof to widely extending subdermal 
cavities ; and an inner layer which forms the outer ends of the choanosomal folds, and 
from which it arises by the suppression, where it occurs, of flagellated chambers below. 
Immediately over the wide apertures of the incurrent canals the poriferous roof alone is 
found. The outer ectosomal layer of the poriferous face is of variable thickness, about 
