ON ZGEAN INVERTEBRATA. 153 
of fine mud, the delicate shells of Pteropoda and Nucleobranchiata are for the 
most part only preserved there. Where the bottom is weedy we find the 
naked Mollusca more numerous than elsewhere ; where rocky, the strong- 
shelled Gasteropoda and active Cephalopoda. Few species either of Mollusca 
or Radiata inhabit all bottoms indifferently. ; 
The nature of the sea-bottom is mainly determined by the geological 
structure of the neighbouring land. The general character of the fauna of 
the Agean is in a great measure dependent on the great tracts of scaglia which 
border it, and of which so many of its islands are formed. The degradation 
of this cretaceous limestone fills the sea with a white chalky sediment, espe- 
cially favourable to the development of Mollusca. Where the coast is formed 
of scaglia numerous marine animals abound which are scarce on other rocks, 
The genera Lithodomus and Clavagella among Mollusca, the Cladocora 
cespitosa among Zoophytes, are abundant in such localities only. 
In a report on the distribution of British terrestrial and fluviatile Mollusca, 
which I liad the honour of presenting to the Association at Birmingham, I 
asserted that a remarkable negative influence was exercised by serpentine on 
the distribution of pulmoniferous Mollusca. This I have had peculiarly 
favourable opportunities of confirming in the Egean, where whole islands 
being formed of serpentine, the almost total absence of those animals which are 
abundant on the islands of other mineral structure is most striking. But I 
found further, that not only does serpentine exercise a negative influence on 
air-breathing Mollusca, but also on marine species. An extensive tract on the 
coast of Lycia and Caria, indented with deep and land-locked bays, is formed | 
of that rock. In such bays, with the exception of a few littoral species 
which live on all rocks, we find an almost total absence of Testacea; whilst in 
correspondent bays in the neighbouring districts, formed of scaglia, of sac- 
charine marble, and even of slate, we find an abundance of Testacea, so that 
it can hardly be doubted that the absence or scarcity of shelled Mollusca in 
such case is owing to negative influence exercised by the serpentine. The 
outline of the coast is evidently an important element in such influences, or in 
modifying it. 
Tides and currents in most seas are important modifying influences. In 
the AEgean the former are so slight as scarcely to affect the fauna; the latter, 
in places, must be powerful agents in the transportation of species and of the 
spawn of marine animals. Their action, however, like that of storms, appears 
materially to affect the upper regions only ; the transportation of the species 
of one region into another seldom extending further than that of the regions 
immediately bounding that in which it is indigenous. Certain species, such 
as the Rissoe, which live on sea-weed, may occasionally fall to the bottom 
region, of which they are not true natives, and may live for a time there, but 
such cases appear to be rare, and the sources of fallacy from natural trans- 
portation are fewer than might be imagined at first thought, and in most 
cases have arisen rather from the form of the coast than from currents. 
Thus where the coast-line is very steep, the sea suddenly deepening to 60 or 
70 fathoms close to the rocks, limpets, littoral Zrocht and other-shells, when 
they die, fall to the bottom, and are found along with the exuvie of the 
natural inhabitants of those depths. Several instances of this occurred during 
dredging. , 
The influx of fresh water, whether continual, or where a river empties 
itself into the sea, or temporary, as on the coast of Asia Minor during the 
rainy season, when every little ravine becomes suddenly filled with a raging 
torrent, bearing down trees and great masses of rock, and charged with 
thick mud, frequently modifies the marine fauna of certain districts very 
