136 
THE VOYAGE OF H.M.S. CHALLEHGEE, 
Genus 3. Astrella, .SoUas. 
The cortex is well developed, consisting of a thick outer layer of collenchyma, sharply 
defined from a thick inner layer of fibrous tissue : the collenchjnna passes into a thin 
fibrous layer beneath the investing epithelium. Pores in sieves. Chones completely 
differentiated, consisting of a main canal lying in the collenchymatous layer, proximally 
constricted into a narrow tube which passes through the inner fibrous layer, distally 
subdivided into several branches, each of which underlies a pore-sieve. The microsclere 
is a pycnaster. 
Astrella vosmaeri, Sollas (PL XYI. figs. 1-5 ; and PI. XL. fig. 8). 
Astrella vosmaeri, Sollas, Prelim. Account, Sci. Proc. Koy. Dubl. Soc., vol. v. p. 193, 1886. 
Sponge (PI. XVI. fig. 1), irregularly prolately ellipsoidal, or compressed cylindrical, 
with rounded edges ; serving as a basis of attachment to Stelletta phrissens. Surface 
hispid, where the spicules are worn away regularly embossed. Oscules not distinguishable 
from the pores. Pores comparatively large, in sieves, generally distributed. Chones 
large, much branched towards the exterior. 
Spicules. — I. Megascleres. 1. Oxea, stout, fusiform, not sharply pointed, 3T38 by 
0‘0592 mm. 
2. Dicliotrisene (PL XYI. fig. 2) ; rhabdome conical, terminating proximally in a 
rounded end about 0’015 mm. thick; protocladi projecting outwards and forwards, 
deuterocladi conical, usually rounded off near the ends, horizontal. Khabdome 3 '02 by 
0’0789 mm., protocladi 0'0876 mm., deuterocladi 0'238 mm. long, chord 0'636 mm. 
3. Anatriwne (PL XYI. fig. 3) ; rhabdome somewhat fusiform, rounded off at the 
proximal end when about 0'006 mm. thick; cladi diverging outwards and only slightly 
backwards for about the first fifth of their course, backwards and only slightly outwards for 
the remaining four-fifths. Ehabdome 3 ‘61 mm. long, 0'0237 mm. thick below the cladome, 
then diminishing to 0'0197 mm., increasing to 0'0276 mm., and finally attenuating to a 
rounded end about O'OOl mm. in diameter; cladi 0‘0395 mm. long, chord 0‘0395 mm., 
sagitta 0'0395 mm. 
II. Microsclere. 4. Pycnaster (PL XYI. fig. 4), a small centrum passing into short, 
thick, obtusely truncated conical actines, from 0‘0118 to 0'0158 mm. in diameter. 
Colour. — Purplish-grey, darker on the upper exposed surface than underneath. 
Habitat. — Station 308, off Tom Bay, Patagonia, January 5, 1876 ; lat. 50° 8' 30" S., 
long. 74° 41' 0" W.; depth, 175 fathoms ; bottom, blue mud. Trawled. 
Remarks. — ^Two specimens of this sponge were trawled, bearing attached to them a 
specimen of Stelletta phrissens, which in the one case is much larger than its support 
(PL XVI. fig. 1), and in the other much smaller. The larger of the two specimens of 
