62 
The. South Australian Naturalist. 
Solemya australis, Lamarck. Notable for the remarkable peri- 
ostracum development. ■ ^ 
Led a crass a, Hinds. 
Area trapezia, Destrayes. 
Glycimeris radians, Lamarck. 
Pinna inermis, Tate and P. tasmanica, Ten. Woods. 
Malleus albus, Lamarck, The hammer-headed oyster. 
Ostrea virescens, Sozverby. ITe Port Lincoln oyster. 
Neotrigonia margaritacea, Lamarck, and varieties, N. dubia 
Sozverby and N. bednalli, Verco. ' 
This bivalve, known only in fossil form in other parts of the 
world, is found living in certain Australian waters. XTtable 
lor its complicated hinge' system, and the beautiful iridescent 
interior. 
Pecten medius,^ Lamarck, The scallop shell. 
Chamys asperimus, Lamarck. 
LICHENS. 
By Ellen D. Macklin, B.Sc. 
There are many aspects of Lichenology, but perhaps ecological 
and biological points prove to be most interesting from a general 
standpoint. Few groups of plants are more important in ecologi- 
cal work than are the lichens. No survey of any district can be 
really complete until its lichen flora has been investigated. They 
are the pioneers in colonisation of many bare rock and soil sur- 
faces, and occur everywhere on the outskirts of the plant woild. 
Even on a single rock one may see all stages in colonisation by 
plant life: the drier exposed parts with their local patches of crus- 
taceous licens; the moister rougher sides covered with fruticiilou^ 
and foliaceous forms, frequently intermingled with mosses; and 
finally the stage where small flowering plants and others, which 
inhabit mere fertile parts, occur. 
A Foliaceous Lichen on Stone. 
There is no habitat, provided growth is possible, that ss too 
hot, too cold or too dry for lichens to grow. They stretch from 
pole to pole, inhabiting desert and mountain tops alike. Lichens 
