218 
THE VOYAGE OE H.M.S. CHALLENGER. 
The resemblance between this species and Caminus vulcani, 0. S., is very close, 
the latter, however, is distinguished by the presence of oxyasters, by the greater length 
of its oxeate spicules (0'076 by 0’016 mm.), and by the larger size of its sterraster (OT mm. 
in diameter). In other respects the spiculation of both is quite similar, in both the 
small globules are present, as also are the orthotrisenes ; these latter I have observ’-ed, 
not only in preparations made by myself from a fragment of the typical sponge preserved 
in the British Museum, but also in Oscar Schmidt’s own slides of mounted spicules 
presented by him to the British Museum. The asters of Caminus vulcani are interesting, 
as they afford another illustration of the passage from an aster with few actines to an 
oxeate spicule with a central tylote enlargement ; the actines are slender and conical, 
sharply pointed, and from 0'035 to 0’039 mm. long. The globule is the same size as 
in Caminus s^phseroconia ; it is frequently produced into a little rounded process on one 
side, remarkably similar to the rudimentary hypha proceeding from the germinating 
conidium of a Penicillium. It evidently indicates a tendency to return to the astral 
form from which we must regard it as derived. 
Subfamily II. Geodina. 
The sterraster is spherical or ellipsoidal ; the somal microsclere is a polyactinose 
aster. In addition to orthotrisenes or dichotrisenes, protrisenes and anatrisenes are 
frequently present. 
Genus 5. Cydonium, Muller. 
The incurrent chones are furnished with cribriporal roofs ; the oscules are the 
uniporal, or more usually cribriporal, openings of excurrent chones which resemble the 
incurrent chones, but are usually collected in special areas without definite margins. 
Cydonium hirsutus, Sollas (PI. XXI. figs. 30-42). 
Cydonium hirsutus, Sollas, Prelim. Account, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 197, 1886. 
Sponge (PI. XXL figs. 30, 31). — Irregular in form, growing into lobes and long, 
irregular, finger-like processes ; bearing in places shallow oval depressions, the floors of 
which are irregularly pitted, but not perforate. The poriferous roofs of the chones are 
thickly distributed in some places, absent in others. Surface in places highly hispid, 
long cylindrical spicules projecting 8 or 9 mm. beyond it ; in other places bare. The 
cortex is thick ; below the outer epithelium with its associated minute spherasters is a 
thin layer of collenchyma, in which the cladomes of the dichotrisenes occur, their cladi 
spreading parallel to the surface, and supporting the poriferous roofs of the chones. 
