PENGELLY — ON THE DEVONIAN AGE OF THE WORT.D. 
843 
formed part of both tlie Silurian and Devonian faunas, was confined 
to a very limited district in each period. 
Blastoidea and Grinoiclea are the only orders of Echinodermata 
found in Devon and Cornwall ; the first is represented by a single 
species, Pentremites ovalis, and this is only met with in the Barn- 
staple area ; it occurs also in the Carboniferous period, as do all the 
other species of the genus. 
Fourteen species of Grinoidea belonging to five genera and two 
fimilies have been found in Devon and Cornwall ; two of these occur 
also in continental Europe in rocks of the same age, and five in car- 
boniferous beds ; bu-^. not one seems to have been derived from the 
Silurian series. Parts of the stems are extremely numerous occa- 
sionally, both in the slates and limestones ; bodies are very much 
less frequently found, and arms seldom if ever. Good examples of 
the body of Hexacriivus interscajnUaris, but without stem or arms, 
have been found in the Woolborough quarry near Newton. 
Excepting Gyp-ldina serrato-striata, found at South Petherwin, all 
the Crustacea of the two counties are Trilobites. No traces of Ptery- 
gotus, Eurypterus, or Estheria — found in other British Devonian 
localities — have been met with. The trilobites belong to ten species, 
seven genera, and six families ; hence the genera and families are very 
limited in specific development. With the single exception of Pha- 
cojps granulatus, found at Petherwin, they all occur in South Devon, 
and are all confined to the Devonian era excepting Plilllipsia Bwg- 
niartii, which is also met with in carboniferous beds in many and 
widely- separated European localities ; this was eminently a carboni- 
ferous genus having no Silurian representative, but in all other cases 
the generic affinity was with the Silurian age. Indeed, the trilobitic 
form of life had passed its culminating point before the commence- 
ment of the Devonian age of the world — the evening of the group 
had already begun : no fewer than a hundred and seventeen species 
had previously become extinct in Britain alone ; of these, ninety- 
eight belonged to twenty-one genera and seven families, which had 
also entirely disappeared from the earth. 
Phacops latifrons occurs in the calcareous slates at Roseland Yale, 
near Liskeard, in Cornwall, where it seems to have attained consider- 
able dimensions : in many cases the eyes, though somewhat flattened, 
are otherwise well preserved, not a facet being scratched. It has 
also been found at Croyde and Barnstaple in North Devon, and in 
clay-slate at Black Hall, near Totnes. 
The tail of Bronteus fabelUfer is by no means rare in the limestone 
of Woolborough, near Newton, and Lummaton, near Torquay ; no 
part of the thorax seems to have been met with, but one example of 
a tolerably distinct head with eyes was found at the former locality. 
Trimerocephalus Icevis, the only British species belonging to the 
genus, occurs under somewhat remarkable circumstances. So far as 
is at present known, it has been found only in one locality, namely, 
on the flanks of a hill called Knowles, near Newton, and no other 
fossil of any kind has been seen there. On this point our knowledge 
