174 THE OCEAN WORLD. 
four. The cells between the chambers are sometimes open in all 
their depth, sometimes more or less shut up by transverse plates ; 
these, being independent of each other, are never reunited in the 
breadth of the visceral cavity, so that they constitute discoid plates 
such as we find in the Zadudar and rugose Madrepores. The animals 
belonging to this group, which may be characterised as stelliform or 
star-like, are very abundant in every sea, and in several geological 
formations. They constitute many genera, among which may be 
noted the Milleporina of Ehrenberg, the polypidom of which Dr. 
Johnston describes as “calcareous, fixed, plant-like, branching or 
lobed, with cells scattered over the whole surface, distinct, sunk in 
little’ fosses, obscurely stellate, the lamelle narrow and almost 
obsolete.”* In Zurbinolia, the animal is simple, conical, striped, 
furrowed externally with larger and smaller ribs, the mouth sur- 
rounded by numerous tentacula, and solidified by a calcareous 
polypidom, which is free, conical, and also furrowed externally ; 
attenuated at the base, but enlarged at the summit, and termina- 
ting in a shallow radiated lamellar cup or cell. Several specimens of 
TL. milletiana have been dredged off the coast of Cornwall, and the 
west coasts of Scotland and Ireland. 
T. milletiana is described as being coral-white, wedge-shaped, some- 
what compressed, with interspaces or ribs equidistant, smooth, and 
glossy. Above, the ribs turn over the edge, and are continued into the 
centre of the enlarged cup, forming its lamelle. “ That the zoophyte 
must have lived for some time after having become a movable thing, is 
proved,” sdys Dr. Johnston, “by the ribs being continued beyond or 
round the point of attachment.” The specimen here described was 
dredged alive ; and Prof. Forbes says of it that “it is a most interest- 
ing and beautiful species, the more so as it is certainly identical with 
Defrance’s Turbinolia milletiana, found in both the crag formations.” 
In the sub-family of the Zoanthidee, the polypes occur in clusters, 
and are multipled by buds, rising from a common creeping, root-like, 
fleshy base ; they thus present a sort of coriaceous polypidom, as in 
Zoanthus (Fig. 59). In the British Channel the species which Dr. 
Johnston has named Z. Couchii, after Mr. Couch, jun., is found along 
the Cornish coast, on flat slates and rocks, in deep water, and from 
one to ten leagues from the shore. It is very small, resembling 
both in shape and size a split pea. When living, its surface is plain 
but glandular, becoming corrugated when preserved. When semi- 
expanded, which is its favourite state, it elevates itself to twice its 
* Johnston’s ‘‘Zoophytes,” vol. i, p. 194. 
