64 SHELL GALLERY. 
tions on bladder-wrack, which, owing to their flexibility, are able to 
adapt themselves to the swaying of the fronds of the Fucus. 
The Selenariidae (Case B 2) form free colonies, usually orbicular 
in shape, convex above and concave below. In Lunulites capulus 
alternating rows of cells and vibracula radiate from the centre of 
the colony. 
Section C. Escharina. — In this group, the front walls of the cells 
are wholly calcareous. Many species form patches or crusts on shells 
etc., and hence the name of the section ; other species, again, form 
stony tree-like growths, or thick plates. Frequently one and the 
same species occurs in the form of crusts or of erect lamellae, the 
identity being recognised by the characters of the individual cells. 
Often a large number of species may be found on one shell. 
Two good examples of this are exhibited in Case A 2. 
€ase A 2. Lepralia pallasiana (Fig. 13) forms sub-circular vitreous patches 
on stones and shells ; the cells are rather large, broadly oval, and 
Fi<r. 13. 
X^?7iFi 
A B 
Lepralia pallasiana, incrusting a shell. A, natural size ; B, cells magnified. 
with the front wall punctured with pores ; the aperture is squarish 
and with a slight indentation on each side. 
Lepralia foliacea forms a massive coral-like growth composed of 
thin contorted plates which fuse to form labyrinthine cavities, the 
plates being constructed of a double layer of cells back to back. A 
large specimen from the English Channel is exhibited in Case B, 
upright part. In Lepralia the orifice and lid of the cell have a 
straight lower margin, but one large group, Myriozoidce, is characterised 
