310 
THE GEOLOGIST. 
Tlironghovit. his paper lie spukc of (liein as "Lower Soulli Devon, Lower 
North Dcvoii, Lower Cornwall, Upper North Devon, and Upi)er Cornwall," 
but slated that he applied the terms " Upi)er" and "Lower" to the rocks of 
Devon and Cornwall as a matter of convenience merely, and not as embodying 
or implying any opinion respecting the co-ordiuatiou of these rocks, with 
deposits of the Devonian age elsewhere. 
Eighty-seven per cent, of the fossil species found in them arc peculiar to one 
or other of the live areas, lianged iu the ortlcr of their sjiecific fossil wealth, 
whether total or peculiar, they stand thus, in descending order : Lower South 
Devon, Upper North Devon, Upper Cornwall, Lower Cornwall, and Lower 
North Devon. There is a greater number of species common to Devonshire 
and the Devonians of strata of continental Europe than to the five areas. If 
the entire number of species found in the district under consideration, be put 
as = one thousand, we have twenty-one derived from the Silurian, eight hun- 
dred and six peculiar to the Devonian, and one hundred and seventy-three 
which passed over to the Carboniferous age. 
The latter part of the paper was occupied with the discussion of various 
hypotheses respecting the cause of the peculiarities of distribution which had 
been described. 
ON THE AVICULA CONTORTA BEDS, AND LOWER LIAS OF THE 
SOUTH OP ENGLAND. 
By Dr. Thomas Wuight, F.R.S.E., F.G.S. 
The object of this paper was to show that the beds known as the "black 
shales with the bone-bea * which rest upon the grey marls of the Keuper con- 
tained a fauna which was special to them, and that many of the sj)ecies were 
identical with those found in the Upper St. Cassian beds of Germany, and the 
Kassen strata of the Tyrol. Dr. Wright described detailed sections of the 
" Avicula cortorta beds" at Garden Clitf, near VV'estbury-on-Severu, which he 
considered as the best type iu England, at Wainlode cliff on the Severn, at 
Aust cliff on the Severn, at Penartli near Cardiff, and at Watcliet near St. 
Quartock's head, the railway cuttings at UphiU and Saltford, and sections of 
the same beds at Binton and Wilmcote, in Warwickshire, were described. 
Nearly the same physical conditions prevailed iu the deposition of all these 
beds. The fauna was limited as to the number of species, but abundant as to 
individuals. I'ccleii T'cilouiensis (JJefr.), Acicula contorla (Fvrtl.), Cnrdium 
rhdicum (Mor.), Polladm arenkola (St rick.), were found in nearly all tJiese 
beds. The " bone-bed" was likewise well exposed in many of these localities. 
The fishes of the " bone-bed" had long ago been referred by Prof. Agassiz, Sir 
PliUip Egertou, to species which were found in the Trias, and the Molluscous 
fauna, as far as it was known iu England, was special to this zone, for these 
reasons mauy geologists consider the " Avicula contorta beds" as the upper 
fossilifcrous portion of the Trias rather than as the basement beds of the Lias. 
The question was an interesting one, inasmuch as fossil mammalian teeth of 
Microkstes had been found in the " bone-bed" of Germany many years ago, and 
recently Mr. Moore had discovered them in a deposit of the same age near 
Frome. 
The liower Lias may be di\ ided into six zones by the ammonites contained 
in each of these sub-divisions; the lowest. No. 1, contains Amnio/iites planorbis 
(Sow.) in great abundance ; this zone is well exposed at Street, in Somerset- 
shire, at Up I^ymc, near Lyme Regis, at Watchct aud Penarth, and in War- 
wickshire and Gloucestershire in several localities, all the fine Enaliosauriau 
