PROCEEDINGS OF GEOLOGICAL SOCIETIES. 
151 
practically by Darwin, in his treatise ' On the Origin of Species,' the ela- 
boration of figures, and the minute details here presented, although ap- 
parently uselessly repeated, may yet assume an aspect of interest which 
they could not otherwise possess. Ostrea intcrstriata {PUcatula of Em- 
merich) of the White Lias, and the small oyster which covers the slabs 
of Lower Lias at Wainload, Westbury, Penarth, etc., associated with 
Modiola minima, recognized by Buckman and other local writers as Ostrea 
liassica, are the earliest known to us in this district. Distinctly gry- 
phoid forms occur considerably higher in the series, and are most abund- 
ant from the zone of Ammonites JBiicMandi, to that in which it is supposed 
to be replaced by Grypli(Ea ohliqua ; but any one who has carefully exa- 
mined these in considerable numbers, and can therefore fully appreciate 
the infinite diversity of form which they assume, rendering the determina- 
tion of the difierences between Oysters and Gryphites exceedingly per- 
plexing, may possibly, in the sequel, feel disposed to adopt the suggestion 
of Quenstedt, that Ostrea liassica may really be the ancestral precursor 
of the species under consideration." 
Six plates of illustrative specimens are given by Mr. Jones, and six 
quarto pages of minute description and comparison. 
The actual vertical range of this species extends, Mr. Jones believes, nearly 
to the base of the Lias formation, and much lower than the beds in which it 
first becomes known to us by the name, hitherto applied to its commonest 
form. " Upon close inspection, almost every specimen of Grypha}a will show 
that it has been in its earliest stage attached, by the flattened or scarcely 
rounded extremity of the beak, to a foreign body, and it is noticeable that 
the symmetrical development of the adult appears to have mainly de- 
pended upon the period at which it became free, the comparative duration 
of which, in various individuals, being indicated by the extent of area so 
rounded or flattened. . . . Upon transferring to paper the outlines of 
that portion of the shell only which could have existed at the time of its 
assuming its liberty, which is easily done by tracing, in well-cleaned ex- 
amples, those lines of growth of which the edges converge at the point 
where the profile curve of the external portion of the true apex commences, 
and from which the lines of the ligamental fossa recede, it will be clearly 
seen that it must once have so closely resembled the young of an oyster, as 
to render it difficult to distinguish the one from the other." Having arrived 
at the conclusion that the young Gryphite must, for a period more or less 
uncertain, resemble an oyster, Mr. Jones's figures specimens to show how 
long such resemblance might endure, and to what extent it could proceed ; 
one of these being attached by a base so large, the upper valve so rugose and 
convex, with ridges following, and corresponding wdth the inequalities of 
the shell upon which it grew^, exhibiting very obscure and irregular con- 
centric lines of growth, and an appearance so completely that of an oyster, 
and different to that of a Gryphite, " that no one," Mr. Jones says, " who 
had never seen similar specimens, in a series of still further advanced 
stages, could admit its relationship in any degree to the latter." 
Could the young animal, by its own volition, free itself from connection 
with the body to which it had attached itself ? This Mr. Jones thinks may 
be answered affirmatively, from the fact, that in the majority of instances, 
that connection could have endured but for a short time. The primary 
point of adhesion must in general have been so small in the young fry, 
and applied to surfaces so even, that a very slight exertion of force of any 
kind, either voluntary or involuntary, would have sufficed to detach it ; but 
it can be readily conceived that in the event of adhesion taking place to 
uneven surfaces, the union between the two bodies must have become so 
