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teeth. From the occurrence of the above exceptions in recent pla- 
cental Mammalia, the example of a like excess in the number of 
molar teeth in the marsupial fossil ought rather to have led to the 
expectation of the discovery of a similar case among existing mar- 
supials, and such an addition to our zoological catalogues has, in 
fact, been recently made. In the Australian quadruped described 
by Mr. Waterhouse under the name of Myrmecobius an approxima- 
tion towards the dentition of the ‘Thylacotherium is exemplified, not 
only in the number of the molar teeth, which is nine on each side of 
the lower jaw in the Myrmecobius, but also in their relative size, 
structure, and disposition. “Lastly, with respect to the dentition, 
Mr. Owen says it must be obvious to all who inspect the fossil and 
compare it with the jaw of a small Didelphys, that contrary to the 
assertion of M. de Blainville, the teeth and their fangs are arranged 
with as much regularity in the one as in the other, and that no ar- 
gument of the Saurian nature of the fossil can be founded on this 
part of its structure. 
With respect to M. de Blainville’s assertion that the jaw is com- 
pound, Mr. Owen stated, that the indication of this structure near 
the lower margin of the jaw of the Thylacotherium is not a true 
suture, but a vascular groove similar to that which characterizes 
the lower jaw of Didelphys, Opossum, and some of the large species 
of Sorex. 
In a memoir to be brought forward on another occasion, Mr. | 
Owen intends to describe the other genus found at Stonesfield, and 
for which, on account of its marsupial affinities, he proposes the name 
of Phascolotherium. 
A notice by R. W. Fox, Esq., was afterwards read, ‘‘ On the 
Formation of Metallic Veins by Voltaic Agency.” 
In this communication Mr. Fox says, that he has succeeded not 
only in forming well-defined metalliferous veins in a crack in the 
middle of masses of clay by means of voltaic agency, but also in im- 
parting to the clay a laminated or schistose structure ; the veins and 
laminee being perpendicular to the voltaic forces. In some instances 
only a pair of plates, or in preference copper pyrites and zinc, were 
employed to produce-the voltaic action ; but a constant battery con- 
sisting of several pairs of plates was much more effective. Among 
the veins thus produced in clay, Mr. Fox mentions oxide and carbo- 
nate of copper, carbonate of zinc, oxides of iron and tin. Veins of 
carbonate of zinc were formed, sufficiently firm to admit of being 
taken out in plates of the size of a shillmg. Mr. Fox then describes 
a vein formed in pipeclay, by Mr. Jordan, by five pairs of cylinders, 
in three weeks. ‘The clay divided an earthenware vessel into two 
cells, into one of which, containing the copper plate, a solution of 
sulphate of copper was put; and into the other, or zinc cell, a solu- 
tion of common salt. Well-defined veins were thus produced of 
carbonate and oxide of copper, and carbonate of zinc parallel to the 
laminz, into which the clay divided; as well as another of carbonate 
and oxide of copper at right angles to them. On dividing the mass 
