in natural history, a large class of fossils, commonly known by the names of Ludus Helmontii and waxen veins.

They are defined to be fossils not inflammable, nor soluble in water; of a moderately firm texture and dusky hue, divided by several septa or thin partitions, and composed of a sparry matter greatly debauched by earth; not giving fire with steel; fermenting with acids, and in great part dissolved by them; and calcining in a moderate fire.

Of this class there are two distinct orders of bodies, and under those five genera. The septaria of the first order are those which are usually found in large masses, of a simple uniform construction, but divided by large septa either into larger and more irregular portions, or into smaller and more equal ones, called talc. The genera of this order are four. 1. Those divided by septa of spar, called fuscumia; 2. Those divided by septa of earthy matter, called geophragmata; 3. Those divided by septa of the matter of the pyrites, called pyritaria; And, 4. Those divided by septa of spar, with an admixture of crystal, called diaphragmata.

Those of the second order are such as are usually found in smaller masses, of a crustated structure, formed by various incrustations round a central nucleus, and divided by very thin septa. Of this order are only two genera. 1. Those with a short roundish nucleus, inclosed within the body of the mass; and, 2. Those with a long nucleus, standing out beyond the ends of the mass.