314 Proceedings of Philosophical Societies. [Aprix, 
which ‘constitutes the basis of the amygdaloid, and which, when its 
cavities are empty, resembles exactly a porous lava; but which are 
most commonly filled with calcareous spar, like the mandelstein of 
the Germans. We find, likewise, a basaltic tuff filled with small 
calcareous pebbles, and containing augite, olivine, mica, and the 
other minerals so common in lavas. _M. Mesnard saw at Beaulieu 
even a hollow which he considered as the remains of a crater. The 
author, after some general reasons against the objections of the 
Neptunists, concludes that this mountain was produced by a sub- 
marine eruption, and that the sea in which it took place continued 
long after to deposit lime-stone. Saussure has already expressed 
himself in favour of that opinion. Faujas has considered it as 
incontestible; and M. Mesnard thinks he sees in it a method of 
conciliating all the opinions about these pretended secondary traps 
so long the-subject of debates. 
Among the numerous remains of unknown animals which fill the 
strata of the earth, there occur marks of an animal of a singular 
form, composed ef a kind of corselet, and of an abdomen formed 
of different segments, each of which is divided into three lobes. 
Naturalists have given them the name of entomolites and trilobites 5 
but they have not sufficiently distinguished them from each other, 
and did not attempt to determine to what particular bed each be- 
longed. 
M. Brongniart, Director of the Manufactory at Sevre, which 
the Class has lately acquired as a member for the section of mine- 
ralogy, in place of the late M. Desmarets, has presented a paper 
on this subject; in which, after a careful comparison of the speci- 
mens that he procured, and likewise of the descriptions and figures 
left by preceding authors, he shows that there exist at least seven 
species of these trilobites; that their principal forms are sufficiently 
different to enable us to divide them into four genera, all of which 
must be arranged in the class of crustacea, and in the order in 
which the branchie are uncovered. The greater number of these 
trilobites belong to the most ancient, that is, to the deepest, beds 
which contain animal remains. They must, therefore, have been 
among the first living beings; and in fact as we approach the surface 
we find crustacea more similar to those which the sea nourishes at 
present; but the trilobites disappear entirely. 
M. Gillet-Laumont, Member of the Council of Mines, and 
Correspondent of the Institute, has exhibited agates containing 
white circles distributed in a quincunx, which resembled some 
petrifaction of a polypus; but they were produced artificially. M. 
Laumont, who had observed that blows struck in a_ particular 
manner detached very regular cones from sand-stone (grés), applied 
the same method to agates, and produced in the same way conical 
fissures, the sections of which presented circles precisely similar to 
those exhibited at first. 
‘M. Cordier has published a memoir on the coal-mines of France, 
and on the progress made in working them during the last 25 years. 
