290 Proceedings of the Royal Society of Edinburgh. [Sess. 
The presence of well-preserved siliceous organisms, the Radiolaria 
and sponge spicules, is another distinguishing feature of this chalk. The 
former probably occurred also in the chalk of the south, and have been 
found by myself in the meal of flints as low as the zone of R. Cuvieri, 
and more rarely in shadowy outlines in the chalk itself ; but in some of 
the Belhelvie boulders they occur in abundance, the delicate network of 
their tests being often beautifully preserved. 
It is not improbable that a junction between the eastern and western 
seas occurred in the early days of the Cretaceous submergence. Mr 
Jukes-Browne ^ has pointed out that the “height attained by the base of 
the Greensand in Morvern shows that the Cretaceous sea must have 
covered considerable areas in Western Scotland,” and, as the lowland 
district was gradually submerged, a strait would be formed between the 
Highlands and southern uplands. If that was so, the straits would 
probably be traversed by currents and the position of the Belhelvie chalks 
may have been near the eastern entrance and the receiving ground for 
terrigenous material and vegetable debris. 
Though one cannot say much with regard to the fragments of chalk 
gathered from the North Sea, the evidence they give is suggestive. Those 
found off the north-east coast of Aberdeenshire show distinctly a con- 
tinuance of the Belhelvie facies, and this with the fact that chalk boulders 
are washed up along the coast north of Aberdeen lends force to the 
hypothesis that there may be an outcrop of chalk covered by the waters 
of the North Sea. 
But a large proportion of these recovered further north in the neigh- 
bourhood of the Shetlands and in the Faroe Channel belong to quite 
another category ; they are pure chalks and must have been laid down in 
clear water away from the influence of mud-bearing currents. Though 
two of these contain Radiolaria, these are preserved only in outline by 
coarser crystals of calcite in a manner similar to those occurring in the 
chalk of the south. 
The great similarity in general structure of the fragments G 1, 3, 5, 
7, 8, 9, 12 to that of the Middle Chalk of England might suggest 
derivation from the southward, yet the occurrence of the same vegetable 
material, which I have never met with in the English Chalk, seems to 
form a link with the chalk of Belhelvie. 
G 2, 6, 14, 15, 16, 21 are chalks differently constituted from any I have 
previously examined. The large size of the spheres and cells, together 
with the peculiar character of the shell fragments, indicates that they 
* Building of the British Isles, 3rd ed., 1911, p. 284. 
