’ 
f 
Part Ii. Szcr. iv.§ 1.] CARBONIFEROUS. 721 
mangrove swamps alluded to already (p. 461). These masses of 
arborescent vegetation, with their roots Spreading in salt water 
among marine organisms, grow out into the sea as a belt or fringe on 
low shores, and form a matted soil which adds to the breadth of the 
land. The earlier coal-growths no doubt also flourished in salt 

ad e 
Fic. 334.—CARBONIFEROUS CORALS. 
a, Zaphrentis cylindrica (Scoul.); 6, Lithostrotion junceum (Flem.), b', Do. magnified 
transverse section, b?, Do. magnified longitudinal section; ¢, Lithostrotion Portlocki 
(Milne Edw.), c', Do. Calyx magnified ; d, Cyathophyllum Stutchburyi(Milne Edw.) ; 
e, Lithostrotion basaltiforme (Phill.) sp. 
water; for such shells as Aviculopecten and Goniatites are found 
lying on the coal or in the shales attached to it. Each coal-seam 
represents the accumulated growth of a period which was limited 
either by the exhaustion of the soil underneath the vegetation (as 
may he indicated by the composition of the fire-clays) or by the 
rate of the intermittent subsidence that affected the whole area of 
o 
Tye’ 
