246 
ELEMENTS OF GEOLOGY. 
malia, among which is Hyopotamus honinus^ differ, so far as 
they are known, from those of the Bembridge beds. Among 
the plants. Professor Heer has recognized four species com¬ 
mon to the lignite of Bovey Tracey, a lower Miocene forma¬ 
tion presently to be described: namely, Sequoia Couttsice^ 
Heer; Andromeda reticulata^ Ettings.; Nelumhium {Nym- 
phoea) doris^ Heer; and Carpolithes Wehsteri^ Brong.* The 
seed-vessels of Char a medicaginula^ Brong., and (7. helicteres 
are characteristic of the Hempstead beds generally. 
The Hyopotamus belongs to the hog tribe, or the same 
family as the Anthracotherium, of which seven species, vary¬ 
ing in size from the hippopotamus to the wild boar, have 
been found in Italy and other parts of Europe associated 
with the lignites of the Lower Miocene period. 
Lignites and Clays of Bovey Tracey, Devonshire. —Surround¬ 
ed by the granite and other rocks of the Dartmoor hills in 
Devonshire, is a formation of clay, sand, and lignite, long 
known to geologists as the Bovey Coal formation, respecting 
the age of which, until the year 1861, opinions were very un¬ 
settled. This deposit is situated at Bovey Tracey, a village 
distant eleven miles from Exeter in a south-west, and about 
as far from Torquay in a north-west direction. The strata 
extend over a plain nine miles long, and they consist of the 
materials of decomposed and worn-down granite and vege¬ 
table matter, and have evidently filled up an ancient hollow 
or lake-like expansion of the valleys of the Bovey and Teign. 
The lignite is of bad quality for economical purposes, as 
there is a great admixture in it of iron pyrites, and it emits 
a sulphurous odor, but it has been successfully applied to 
the baking of pottery, for which some of the fine clays are 
well adapted. Mr. Pengelly has confirmed Sir H. De la 
Beche’s opinion that much of the upper portion of this old 
lacustrine formation has been removed by denudation.f 
At the surface is a dense covering of clay and gravel with 
angular stones probably of the Post-pliocene period, for in 
the clay are three species of willow and the dwarf birch, 
Betula nana^ indicating a climate colder than that of Devon¬ 
shire at the present day. 
Below this are Lower Miocene strata about 300 feet in 
thickness, in the upper part of which are twenty-six beds of 
lignite, clay, and sand, and at their base a ferruginous quart- 
zose sand, varying in thickness from two to twenty-seven 
* Pengelly, preface to The Lignite Formation of Bovey Tracey, p. xvii. 
London, 186k 
t Philos. Trans., 1863. Paper by W. Pengelly, F. K. S., and Dr. Oswald 
Heer. 
