The classification of the British Ordovician Rocks has gone through many phases of instability in the past, and at the present time seems to be passing through another such phase. There are probably many causes contributing to this state of things, two of which seem to be fundamental; the first, the differentfacies of development exhibited in different districts by the formations making up the system; the second, the varied elements entering into the composition of the shallow water faunas apart from the considerations of facies; these would seem to be governed largely by possibilities of migration into the British region of the Lower Palaeozoic geosyncline from different directions, i.e. from America, from Northern Europe, and from Central Europe, so that a different type of “shelly” fauna characterizes the north-west and south-east margins.

In a paper published in 1929 on “The Basal Complex of Jamaica, with Special Reference to the Kingston District” (Matley, 1929, 440–92) I gave an account of the nature and structural relationships of a complex of rocks consisting partly of plutonic rocks (granodiorite and serpentines) and partly of metamorphosed igneous and sedimentary rocks, now chiefly in the condition of amphibolites, hornblende- and chlorite-schists, quartz-sericiteschists, and marbles. The paper, which contained an important Appendix by F. Higham on the petrography, presented the results of many months' arduous work in the field, including the detailed mapping of the Kingston District, for which a good contoured map as available on the scale of 2½ inches to the mile. The geology of the area is so difficult that, in my opinion, the only way of arriving at sound conclusions is by adequate field-mapping.

While examining the collection of Old Red Sandstone fishes in the Royal Scottish Museum, the writer found the frontoethmoid shield of a Crossopterygian fish, from Eoghole, on the Muckle Burn, near the boundary between Elginshire and the county of Nairn. Though imperfect, the skull fragment retains its natural shape, and at once recalled the similar region of Eusthenopteron, from the famous fish-bearing beds of Scaumenac Bay, Province of Quebec, Canada. Further comparison seems to prove the generic identification. The stratigraphical relationships of the find are known with some precision, and the implications are of considerable importance. It is especially opportune that Dr. Erik Jarvik, of Stockholm, has just finished an account of Eusthenopteron species from the Baltic and Russia, with a discussion of the stratigraphy of those localities which yield the fish. Certain features of the Canadian Eusthenopteron are discussed in the present paper for comparison with the Scottish form: this is in no way prejudicial to the monograph on the Scaumenac Bay material, now in preparation by Dr. Jarvik.