High Cases 
IV.-VI. 
32 
GUIDE TO THE CORAL GALLERY. 
Monaxonida (Monaxon Sponges). 
This Order contains by far the largest number of species. The 
skeleton-spicules are uniaxial, i.e., shaped like rods, like needles 
pointed at one or both ends, or like pins ; six-rayed and four-rayed 
spicules never occur. The spicules may be scattered or united into 
bundles, and may form radiating or reticulate scaffoldings. Flesh- 
spicules may or may not be present, one of the most common forms 
being buckle-shaped (Fig. 17). The huge Neptune’s Cup Sponges, 
Poterion patera (on pedestals), from the East Indies, are among the 
largest of Sponge forms ; the skeleton is composed of a dense net- 
work of bundles of pin-shaped spicules. 
The large specimen of Poterion placed above the Hexactinellid 
Case, and formed of three trays one above the other, belongs to a 
closely allied species. 
The Boring Sponges, which also have pin-shaped skeleton 
spicules, are remarkable for their habit of boring into shells and 
limestone. 
Cliona celata (Case IY. 3) is very common in oyster shells, in 
which it excavates extensive lobed galleries ; the oscules and groups 
of pores are situated on conical elevations which project through 
small holes in the surface of the shell. Vigorous specimens burst 
through the shell and form large cork -like masses (Case IV. 3), 
the identity of which with the boring portion was for a long time 
unsuspected. The magnificent specimen of Gaulospongia verticillata 
(Fig. 15 ; Case IY. 2) has a thick main stem branching into three, 
the stems giving rise to closely-set whorls (or spirals) of thin lamellae 
gradually diminishing in size from below upwards. 
The massive Suberites ivttsoni (Case IY. 3) is remarkable for its 
brilliant purple colour. The colouring matter forms a rich purple 
solution in acidified alcohol. Esperiopsis cliallengeri (Fig. 16), from 
825 fathoms, east of Celebes (specimen in fluid, Case IY. 4), one of 
the “ Challenger ” treasures, has a main stem giving off along one 
edge a series of stalked bowl-shaped fronds increasing in size from 
below upwards. The in-current pores are situated in the concavity, 
and the minute oscules on the convex surface of each bowl. 
The series of specimens- of Echinonema typicum (Case IY. 4) 
shows well the great variation in form that may occur in one and 
the same species. 
Fresh-water Sponges (Case YI. 3, facing west) are common 
