vi INTRODUCTION. 
has been but inconsiderable ; these latter belong chiefly to Ancliff, and to the vicinity of 
Scarborough. ‘The parallelism of the deposits at the two former places would appear 
to be well ascertained, but with respect to the rocks which are so extensively exposed 
upon the coast of Yorkshire, although the evidence of geological position appears to 
be satisfactorily determined, they possess but few mineral features which serve to connect 
them with their supposed equivalents in Gloucestershire, Wiltshire, and Somersetshire ; 
they constitute a great carboniferous deposit of the Oolitic period, abounding with land 
plants, and containing intercalated bands or thin beds of dark gray argillaceous shales, 
limestones, and sandstones, containing marine shells, of which only a minority of species 
have been identified in other localities. The evidence afforded by the few species of 
univalves which have been forwarded to the authors from Scarborough, through the 
kindness of Mr. Bean, though not conclusive, tends rather to assimilate them with the 
Inferior Oolite ; and it will be perceived on consulting the table of species at the end of 
the Monograph, that of the twenty-one Yorkshire species, none have been identified with 
Great Oolite shells of Mimchinhampton or Ancliff, but that seven agree specifically with 
Inferior Oolite shells of the Cotteswold hills. The Yorkshire deposits to which these 
remarks refer constitute the entire series of plant-bearmg beds numbered 11, 12, and 13 
in Phillips’s ‘ Geology of Yorkshire,’ reposing on No. 14, or the Dogger, which is proved by 
its fossils to be the equivalent of the Inferior Oolite, or at least to a portion of that 
formation. Admitting, therefore, the parallelism of the deposits contaimimg somewhat 
distinct Faunas, in the north-eastern and south-western parts of the present area of 
England, we are naturally led to infer, either that the physical conditions might be favor- 
able to the continuance of species in one locality, or that species characteristic of an older 
deposit, in a more distant region, may have migrated and lived on during the formation of 
a newer deposit in another, the conditions having become unfavorable to the perpetuity 
of their development in the latter deposit over the original region whence they had 
migrated.” 
For the above-mentioned reasons, it has been deemed desirable to separate the 
1 The section at Ancliff, near Bradford, is as follows : 
Rubble . 5 feet. . . Abounding with Polyparia. 
Soft Oolite 15 ,, . . This is the bed celebrated for the Ancliff fossils. 
Clay - 1 ,,  . . Containing small sponges, and many fragments of shells. 
Rag - 63 ,,  . . Very coarsely Oolitic. 
Soft Oolite 5 ,, 
From Mr. Lonsdale’s interesting memoir, “On the Oolitic District of Bath,” in the ‘Geol. Trans., 
p- 252, in which many other sections of the Great Oolite are given, and the range of the deposit in that 
neighbourhood is accurately traced. 
* Unfortunately the entire character of the fauna of the Great Oolite in the centre of England is not 
well ascertained, nor is the range and extent, southerly, of the fluvio-marine conditions of the Yorkshire 
Oolite accurately determined. As bearing on this point, the reader is referred to a paper by Captain 
L.L. B. Ibbetson and Mr. Morris, “On the Geology of Stamford” (‘ Brit. Assoc. Rep.,’ 1847, p. 127). 
The subject of migration of species, during the Oolitic epoch, is ably treated in a valuable memoir by 
M. Gressly, ‘Observations Geologiques sur la Jura Soleurois.’ 
’ vol. iii, 
