It is curious how readily the public misconceives even the most simple of scientific problems. A plausible theory, no matter how fallacious, will gain an immediate currency which it is difficult to undermine until it has run its course. Such theories do harm to the public, to industry, and to science, and they should be combated rather than avoided, so that the mischief may be curtailed, if not entirely eliminated.

The strong shock of January 14, 1919, originated in a region from which earthquakes have been absent for many years, perhaps for several centuries, and its interest is therefore increased by the fact that it was a twin-earthquake, that is, one produced by a single generative eifort in two detached foci.

The Corwen gravels were described by D. Mackintosh, forty-three years ago, in a paper “On the mode of Occurrence and Distribution of Beds of Drifted Coal near Corwen, North Wales”. He attributed the gravels to an interglacial marine submergence and claimed that the coal found in them was derived from the outcrop of Coal-measures near Kuabon, twelve miles due east of Corwen.

In Megacystis the periproct—which S. A. Miller always called the moutn—lies between adoral circlets II and III, being bounded by the two posterior facet-bearing plates and the posterior interradial, i.e. 3 of Adorals II, also by 2 or 3 of Adorals III, making 5 of 6 plates in all. The number 5 is the more usual; it occurs in M. aspera. faberi, gorbyi, indianensis, ornatissima, ornata, parcula, parca, perlonga, plena, scitulus, and spangleri, also in British Museum specimens E 7631, —33, —35, —37, —38, ?—39, —40, —42, —44, —45, —74, —76, —77, E16167, and E 16168 (see our figs. 24, 25, antea). The number 6, due to an additional Adoral III, is found in M. baculus, commoda, splendens, and perhaps gyrinus, also in E7630, —34, —36, ?—75, and E 16171 (see our figs. 22, 23, 28, 30, antea). This does not seem to be a difference of such constancy as to be relies on for the discrimination of species. It is the sole character distinguishing Miller's M. commoda from his M. gorbyi, not to mention M. scitulus and M. parva, which may be younger stages of the latter species. Similarly such specimens as E 7631, E 7635, E 7638, and E 7644, each with 5 plates, cannot otherwise be distinguished from E 7636 with 6 plates; while E 7630 and E 7634 with 6 plates are otherwise the same as E 7633, E 7640, E 7642, E 7677, and E 16168, each with 5 plates.