Pvn H,i I'UitlS

2 BRACHIOPODA. *
lineage.
The Lingula-hed of the upper Cambrian system
is well known ; and other palaeozoic strata contain
equally rich mines of similar wealth. But although
the number and variety of recent Brachiopoda are not
equal to those of former days,
the difference does not
appear to be so great as has been usually represented.
Mr. Davidson, who is perhaps the greatest authority on
the subject, says that there are 20 Silurian, 25 Devo-
nian, 19 Carboniferous, 12 Permian, 12 Triassic, 14 Ju-
rassic, 12 Cretaceous, 10 Tertiary, and 14 recent genera
and subgenera; so that we seem to have improved
in this respect on the middle ages, and future generations
may exhibit a further advance, and even rival the
primeval era. The comparative rarity of Brachiopoda
in modern times may be easily accounted for. They
mostly inhabit rocky and stony parts of the sea-bed,
which cannot be reached by the dredge without great
risk of its being lost or injured, although they are gre-
garious and occur in vast numbers under favourable
circumstances. My late friend, Dr. Lukis, found more
than 200 specimens of Argiope cistellula on a single
stone brought up from a depth of 20 fathoms off Guern-
sey; and I have myself repeatedly
taken Terebratula
caput -serpentis and Crania anomala in such profusion
on the western coasts of Scotland, as to be compelled
by a sheer embarras des richesses to throw many
hundreds overboard in the course of a day's dredging.
Even the comparatively rare T. cranium is no exception.
I have counted seventy specimens, although broken and
imperfect, which came up in a single
haul off the Shet-
lands. Terebratella Spitzbergensis, which was at first
accounted extremely scarce, now appears, from Dr. Otto
Toreirs researches, to be by
no means uncommon in its
native haunts ; and I lately picked up two or three fossil