PETROGENIC problems concern the processes and effects of adding to magma, or subtracting from it, rock-forming substance in general. Increment or loss of silica alone entails relatively simple mineralogical consequences. The more intricate problems concern the addition of associated material (notably alumina, the Ro-oxides, alkalies, and fluxes) in varying relative proportions, and at any stage in the evolution of rest-magma. These additions tend either to promote, counter, or otherwise modify the prevailing trend of differentiation in magma thus augmented.

IT has been said that there is no bad beer, but some is better than other, and this dictum holds, I think, for bibliographies of the foraminifera. Dr. C. D. Sherborn’s well-known Bibliography (down to 1888) and his Index to genera and species (down to the end of 1889) set a standard that has not been maintained in later bibliographies. Finding a slip or omission in these two works one feels with Little Jack Horner “ What a good boy am I! ”.

Sula Sgeir consists of hornblende-gneiss with occasional biotite and augite. The whole is intersected by small pegmatite veins which merge along the borders into the gneiss. Though evidence is small, it seems probable that the island, together with North Rona, came under the influences of the Quaternary ice.

The Flannan Islands consist also of hornblende gneiss, biotite being a fairly common accessory. Numerous and varied pegmatite Veins occur throughout the islands, and in certain cases have affected the foliation of the gneiss. Owing to the proximity of the islands to the Lewis and the Harris, and the presence of adeposit of cemented sand on Eilean Ghobha, it seems probable that the Quaternary ice also reached these islands.

GUTENBERG is not a geologist but, as a geophysicist, he is directly interested in several of the broader questions of geology. He has been impressed by the simple way in which Wegener’s drift theory seems to solve many geological problems, but he finds it impossible to accept that theory in its entirety. He has, therefore, tried to formulate another theory which is more in accordance with geophysical data, and which still solves the same geological problems. “Continental Spreading,” a name suggested by Dr. Harold Jeffreys, expresses very clearly its dominant feature.

THERE has been considerable uncertainty about the true characters of the species Illaenus bowmanni Salter, and many foreign palaeontologists have consequently found it difficult to institute a close comparison of it with other species and have suspected its composite nature. As Holm and Warburg have remarked, the species is badly characterized, and some important critical features, such as the shape of the caudal fascia, are ill-defined or not clearly described in the definitions or well represented in the figures. The poorness of the specimens is largely accountable for these omissions. A recent detailed investigation which the author has been enabled to make of the specimens used by Salter, Portlock, and McCoy in drawing up a definition of the species, together with the examination of many other specimens ascribed to it from the original and other localities, throws some useful light on the subject and helps to clear up some of the obscure points, but it also shows that most of the earlier and current synonymies and references which have been published from time to time are untrustworthy and inaccurate.