422 
THE GEOLOGIST. 
incurva in profuse abundance ; an occasional thick cast of Homomya, 
and Cardinia lAsteri, with its varieties hylrida and imlricata ; all these 
often imbedded in fox-coloured ragstoncs of indurated clay ; then Lima 
gigantea, in bright and beautiful specimens, exceedingly prevailing in 
the bands of limestone ; Lima antiquata, Pentacrinus tulerculatus, Pinna 
folium, Peden, Jvicula; two species of Ammo7u'tes, in the state of broken 
and undefinablc casts ; a Unicardium, a large oval Cardinia, fragments 
of wood, microscopic round-mouthed Terehrcs., spines of sea-urchins, 
masses of Vcrmetus ; a single Canjophijllia f? J, Ostrea minima (syn. 
Liassica), Modiola minima, and a larger species, and slabs extremely 
crowded with the larger Posidonomga (so called by the late Mr. Strick- 
land), which is here found associated with the small Modiola and 
Cardium VnoLi accompany it in the south. The " Posidonomya-bed" can 
be better examined at Hotham than at any other place with which I am 
acquainted. About Coombo Hill, in Gloucestershire, this fossil may 
occasionally be found lying on tlic plouglied lands, but chiefly as a cast, 
and in a bouldcrcd state, whereas, at Hotham, it occurs in dense layers, 
and in every state of growth, imbedded in a very fine-grained, dark -blue 
stone, of a whitish colour externally, the sections of which exhibit lines 
indicative, sometimes, of a very gently rippled, and, sometimes, a most 
peaceful lamination. This bed makes excellent roadstone, being 
very hard and intractable, and splitting rather vertically than in the 
direction of its deposit. The dense layers seldom contain any 
other shell besides the Posidonomya, though there is, at times, 
an admixture, in subordinate numbers, of the characteristic Cardium 
and Modiola of Gloucestershire. One slab in my possession, not two 
inches thick, is exclusively occupied on one side with Posidonomya, 
and on the other with the Cardium and Modiola, The former of 
these shells is very difficult to bo detached from its matrix in a 
perfect state. Portions of it may be obtained for microscopic 
examination, but as yet I have never seen the hinge. 
I was deceived by this stratum into the expectation that I might, 
perhaps, find the "Bone-bed," and "Insect-bed" in this range at 
Hotham. The Lowest Lias may be seen in the marl-pits, passing con- 
formably into JTew Ecd Sandstone, by alternating layers of Lias and 
sand disposed horizontally in slightly-wavy lines. This transition is 
apparently abrupt and sudden, and is completed in a very few feet, so 
that we have beds of fiao, red-coloarcd sand hastily exchanged for 
