FOSSIL DIATOMACEZ. 935 ° 
of Algz, and a few grains under the microscope yield a 
great variety of exquisite forms: figures of several are 
given in Lign. 4, from specimens of this earth, with which 
I was favoured by the Countess of Caledon. They com- 
prise two or three species of Navicula, Galionella, Cosci- 
nodiscus, Gomphonema, Bacillaria, Stauroneis, &c., and 
spicules or spines of fresh-water sponges.* 
Beds of siliceous marl—that is, of argillaceous earth 
combined with a large amount of minute particles of 
silex, all of which prove to be organisms when examined 
by a high magnifying power,—have been found in nume- 
rous places not only in England, but all over the world, 
since M. Ehrenberg first directed attention to their nature 
and origin. 
Near Bryansford (Newcastle), Binstwick in Holderness, 
and in the Fens of Lincolnshire and Cambridgeshire, ex- 
tensive fresh-water microphytal deposits have been disco- 
vered and examined. 
From our Antipodes I have received many examples of 
these vegetable earths. My eldest son, Mr. Walter Mantell, 
discovered an extensive bed of white marl on the banks of 
the great brackish-water lake of Waihora, in the middle 
island of New Zealand, consisting entirely of frustules of 
Bacillariz. From New Plymouth he obtained some new 
and exquisite forms of Navicula, Stauroneis, é&c.; ranges 
of low hillocks of sand, of considerable extent, being made 
up of microphytes (microscopic plants).t 
Mr. Dean, of Clapham Common, informs me that a 
* The names of the usual kinds of Diatomaceous frustules may be 
learnt by reference to Mr. Andrew Pritchard’s abstract (with coloured 
figures) of Ehrenberg’s Infusoria. The splendid work of Mr. Ralfs, on 
the British Desmidiex, 1 vol. 4to, with coloured plates, is the best 
guide for those who wish to study the recent plants. 
t+ See a Memoir on the Geology and Fossil Remains of New Zea- 
land, from the researches of Walter Mantell, Esq.—Geol. Journal, 
vol.-vi. pl. 29. 
