—— -_ —<. 
189 
investigation to which the Cotteswold Club may advantageously 
apply itself. As we have already seen in the case of the junction- 
beds between the Iuias and the Inferior Oolite, so we see here 
exemplified, those mixed characters partaking of the features of 
two contiguous formations, which renders it very difficult to draw 
a line of demarcation, and to assign to each its exact share in 
the beds in question. Looking merely to mineralogical character, 
a casual observer would at once place his finger on the well- 
marked line of junction, where the “Red Marl” is opposed in 
strong contrast to the dark overlying clays in contact with it, 
and would, without hesitation, allot the one to the Trias, and the 
other to the Lias. But an examination of the fossil contents of 
the beds, as enumerated above, will lead to a very different 
conclusion. 
The Bone-bed, which occurs about the middle of the series, 
is charged with vertebrate remains of a decidedly Triassic 
character; though in many localities the vertebrate remains of 
the bone-bed continue upwards in part into the blue stone of 
Ammonites planorbis above, and are even found in a separate liassic 
bed. Fossilremains of a similartypeare met with at Westbury in 
the lowest band of the dark clay in immediate contact with the 
“ Red Marl,” and they are traceable upwards in the beds num- 
bered 2 and 7 respectively. With No. 7, which immediately 
overlies the Bone-bed, we lose all further traces in this Section 
of these peculiar records of vertebrate existence, and after the 
interposition of eight feet of clay, the lighter colour of which 
may perhaps vindicate a mineralogical change in the circum- 
stances of its deposition, we arrive at a very remarkable band 
which is characterised by the presence of Estheria, and from that 
circumstance is designated the Estheria-bed. This fossil, which 
was formerly considered to be a bivalve Mollusk, and as such 
received the appellation of Posidonia minutia, is now transferred 
to the Entomostraca, though with some doubts as to whether it 
be correctly referred to that Order of Crustaceans. Should such 
be the case, it may possibly suggest for it a freshwater habitat, a 
circumstance in some degree supported by the discovery by Mr. 
Brodie of Cypris, plants, and Cyclas in the limestone-band No. 
13 which overlies it. 
In the Journal of the Geological Society for November, 1856, 
Mr. Rupert Jones writing upon Estheria minula, observes that, 
« Although the recent Estheria is a Marine Crustacean, yet since 
very closely allied forms are of fresh water habits, andsince among 
bivalved Entomostracans, different species of a genus, and even 
the individuals of a species, occasionally live either in marine or 
in fresh water, there is no certain evidence afforded by the fossil 
in question whether the so-called Triassic deposits in which it 
is found were formed in rivers, lakes, or seas.” According to 
Mr. R. Jones different species of Estheria are met with in 
Vou. Ir. T 
