THE terminology used to-day by British writers on Rugose corals is founded on the first competent terminology ever formulated, that of Henri Milne Edwards and Jules Haime, which was published in 1848, and added to during the following twelve years. These eminent French workers evolved a general terminology for corals as a whole and a special one for the sub-order Madreporaria Edwards and Haime. Their researches were more exact than those of their predecessors and called for more exact terms. Dana also realized the need for an exact terminology and introduced one some two months later (1848, p. 723); but it was less complete, less coherent, and less precise than that of Edwards and Haime, and has not been generally adopted by later writers.

Pebble-Like aggregations of calcium carbonate have been described from certain lakes in the northern United States and southern Canada under such names as squaw biscuit, marlyte, and marl balls. The most northerly of the previous records of these structures in eastern Canada, known to the writer, cites them from Emerald Lake, a small Ontario lake in latitude 47 degrees. Structures of this type are known to be products of the growth activities of certain species of the blue-green algae. Those from Canandaigua Lake, New York, have the hardness of limestone and most geologists would be likely on casual examination to class them as flat water-worn pebbles of Palaeozoic limestone. Others, such as those found in Mink Lake, near Ottawa, Canada, are much softer and less compact than limestone.

The two chief difficulties in taking serial sections are to ensure that the successive sections are all parallel to each other and to obtain reliable drawings of them.