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DEFORMED DIATOMS. Iig 
alluded to above, but remarkable in this instance for the 
curious distortion of shape in the majority of the frustules, 
the extent and variability of which may be seen by the 
accompanying diagram. Every student of diatoms must 
occasionally have come across deformed or modified valves, 
in which, while the specific distinctions were unmistakeable, 
the general appearance was very considerably altered. Dr. 
Miquel, in an article in ‘‘ Le Diatomiste,’”’ professes to have 
effected modifications in the diatomaceze by artificial culti- 
vation, the predominance of certain physical and chemical 
elements being intentionally exaggerated. 
In the case under notice, the deforming agent may have 
been the deficient amount of light in the Subway, or it may 
be that the diatoms are in some way affected by infiltration 
of brackish water from the dock, though the normal form is 
not uncommon in brackish water. In any case, the variations 
of form are unusual and worth notice. 
Considerably more than fifty per cent. of the specimens 
collected are deformed in this way. 
TooTH OF OXYRHINA MACRORHIZA FROM THE RED CHALK 
or SpEEToN.—Mr. F. Lamplough, on a recent excursion, 
obtained a very fine shark’s tooth from the Red Chalk near 
Speeton Gap, which appeared to be different from anything 
that the writer had seen from the Red Chalk of Yorkshire. 
On sending the specimen to Mr. A. Smith Woodward, F.R.S., 
of the British Museum, that gentleman informs us that the 
tooth belongs to the shark named Oxyrhina macrorhiza by 
Pictet and Campiche, and that he only knows the species 
from the Gault and Cambridge Greensand and from the 
Albian of France and Switzerland. The tooth is, therefore, 
an addition to our Red Chalk fauna. A figure of a similar 
specimen from the Cambridge Greensand appears with Mr. 
Woodward’s paper on ‘‘ Notes on the Sharks’ Teeth from 
British Cretaceous Formations,” which appears in the Pro- 
ceedings of the Geologists’ Association, Vol. XIII., No. 6, 
for February, 1894, Pl. V., fig. 24.—T. Suepparp, F.G.S., 
Sept., 1900. 
