Letter Mr Borodich to Professor Jameson. 385 
followed a rough track, on the margin of shallow cliffs of alter- 
nations of tufa and basalt, for about a mile and a halt, when we 
reached a depression, more like a basin than a plain, covered 
with a deep bed of loose and agglutinated sand. These sands 
have in some degree been fixed or bound by the numerous 
branches of forest-trees they have enveloped ; for these branches, 
(which have preserved their lateral twigs), are so numerous, 
that they are spread over the surface, as well as beneath it, like 
a net-work of stoloniferous roots. It is scarcely possible to set 
the foot to the ground without treading on them. Both the 
branches and the trunks, (which stand on their roots in their na- 
tural position), are incased in a thick hard sheath of aggluti- 
nated sand, which has followed the external configuration of the 
wood like a cast. In some instances the wood has entirely pe- 
rished, and the envelopes are found void, like tubes ; but most 
frequently the wood is found within, as a distinct mass, and has 
become sufficiently siliceous to scratch arragonite (Figs. 108, 
109*). The tallest fragments of trunks reach about a foot above 
the surface of the sand ; how far beneath it 1 cannot say. There 
were two or three as thick as my body. Sometimes imbedded in 
the envelopes of the wood, but generally in the loose sand of the 
surface, were innumerable fossil shells, intermingled promiscu- 
ously ; two species terrestrial ; the third belonging to a marine 
genus. 
The Delphinula, Fig. 110. a, b } is the DeJphinula sulcata of 
Lamarck, only known in the fossil state, and found at Grignon. 
But the Helices belong to the group Lamellatae of De Ferus- 
sac’s sub-genus Helicostyla. The smaller species Fig. ill. is 
globose, but the larger, Fig. 112. a , b , c, (which is Jth inch in 
its greatest diameter, and T 7 5 th deep), has the last whorl com- 
pressed or flattened. There are several helices still smaller than 
the former, with the umbilicus exposed ; but this is merely be- 
cause the plate which covers the columella is not entirely de- 
veloped, and I have not the least doubtof their being young shells 
of the first-mentioned species. These shells are perfectly dis- 
tinct from the existing helices of Madeira, (Figs. 38, 39, 40. 43, 
44.), of which there is not one to be found in the neighbourhood. 
* These, and the other Figures noticed in this page, refer to drawings in 
the author’s possession. — Edit. 
VOL. XI. NO. 22. OCT. 1824. b b 
