Professor Reynolds has recently described from one of the Arnold Quarries, Chipping Sodbury, a section in which several beds of the Carboniferous Limestone were seen individually to be thrust over, or underthrust by, Rhaetic deposits (Text-fig. 2).1 No decision was made as to the origin of this structure.

Through the kind intervention of Dr. R. Rutsch, of Basle, who himself is interested chiefly in the Tertiary mollusca of Trinidad, I have recently been able to study some tolerably well-preserved ammonites from beds in the Northern Range which have long been the subject of discussion. The ammonites had been already recognized by the Trinidad geologists as Upper Jurassic and bore the provisional identification: “Idoceras sp.,” which would have indicated a Lower Kimmeridgian age; but since confirmation of this seemed desirable, I was asked to see whether the ammonites were determinable, and if so to publish a note on the results of my investigation.

Watson (1937) in his important work on Acanthodians demonstrated that the mode of jaw-suspension of this group and probably also that of the Arthrodira.Macropetalichthyida, Rhenanida, and Antiarchi was in a more primitive condition than in other Gnathostomes. The hyomandibula of these fishes played no important part in the suspension of the jaws, and the hyoidean gill-slit persisted as such, not being reduced to a spiracle. Watson introduced the name Aphetohyoidea (free hyoid) for the group containing all these fishes, distinguishing them from the more advanced Chondrichthyes and Osteichthyes.

There can be little doubt that most petrologists will welcome J- the classification of igneous rocks according to their grainsize as proposed by the British Association Committee on Rock Nomenclature and Classification (1). This classification has been incorporated in the new edition of the well-known textbook of Hatch and Wells (2) and has recently been very ably defended by Wells (3). To avoid misunderstanding it must be emphasized that grain-size is taken to be only one of the factors in the classification of igneous rocks and not the sole factor, and that the suggested limits between different grades of granularity must be taken at the present time to be only provisional.

This note is prompted by the recent discovery (by Mr. R. Casey) of ammonites of the jacobi zone at the base of the Folkestone Sands.1 These ammonites include A. jacobi itself and since, more-over, the jacobi zone is likely to be much quoted, it seems particularly desirable to inquire whether the name jacobi can be safely used.