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C. CROSSLAND—PHYSICAL DESCRITTION OF KHOR DONGONAB. BOO) 
mostly sand, as is the maritime plain, the surface of the deposit containing an 
undue proportion of stones owing to removal of loose sand by the wind. 
The sides of this gravel ridge were once the sea-shore, the sand plain, ike 
the well valley, being of marine origin as evidenced by numerous marks of 
old beach lines running more or I#ss parallel to the curves of the present shore 
line, and, in one or two places, by outcrops of coral. Numerous modern sea- 
shells strew the surface, A/urex ramosus and Strombus sp. being the most 
common, while, by digging, many smaller and more delicate species are turned 
up, the proof of the marine origin of the ground, not only its surface, being 
thus complete. 
Detailed Description.—The plain has several peculiar features which make 
its description, and the explanation of its formation, worthy of attention. Along 
its seaward edge is a band of sand hillocks one to three feet high formed by 
the collection of blown sand among and to leeward of tufts of the Halophyte 
Suaeda Volkensi * (see Pl. 80). ‘This wonderful plant is able to preserve a 
touch of brilliant perennial green in these fearful wastes, where there has 
been practically no rain for four years, and in autumn is still splendid with 
the crimson bracts of its flower-spikes. Its succulent leaves remain fresh, 
notwithstanding the storms of summer which dry all moisture from ordinary 
vegetation like the heat of a fire and which dull glass by the rasping of the 
driven sand grains. Within this zone, which is about ten yards wide, the 
surface is almost perfectly bare and level. There is no loose sand, and though 
at first the surface is soft like soil, or hard and friable as though frozen 
according as the weather is damp or dry, a little distance inland it becomes 
nearly as hard as a macadamised road. There are areas of exceptional hard- 
ness, where the surface is more like stone than sand, and can onl y be broken 
by chisel or crowbar. These are generally found in bands which more or less 
follow the curves of the shore line, and represent the tops of ancient beach 
lines. They are chosen by the natives as sites for their houses, providing 
clean hard floors ; one area was so perfectly smooth and large as to provide 
us with an excellent tennis court. The third and innermost section is nearly 
as broad as the second, and here the general level is raised and the surface 
made undulating by the collection of dry sand by two species of salt-loving 
desert grasses 
prickly leaves, almost like furze prickles, and especiaily by its globular white 
flower-heads on slender stalks; an inner band of another prickly grass which 
is, however, more of the ordinary gramineous form. Both propagate by 
an outer band of Hluropus villosus, recognised by its grey 
* Suaeda generally occurs alone, but in places other Xerohalophytes occur. The latter are 
species very abundant as a fringe round the high-water line of all the sandy islets where 
Suaeda is very rare or quite absent. hese islets are formed of broken shell and coral, the 
plain of inorganic sand. 
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LINN. JOURN.— ZOOLOGY, VOL. XXXT. » 
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