Summary The Speeton Clay (Berriasian to Lower Albian) contains a much fuller succession of early Cretaceous coccoliths than has been described from beds of this age elsewhere. Most of the species are confined to the Lower Cretaceous and belong to three families which show a vigorous diversification in the Speeton Clay. Many of the rarer species are the forerunners of forms that are abundant in the Upper Cretaceous. There is a substantial break between Upper Jurassic and Lower Cretaceous assemblages, with very few species crossing the boundary. In the Berriasian beds a new flora begins to develop, very largely from Jurassic families. Most of these early forms are confined to the Speeton Clay and the first substantial appearance of Gault species is not until the Hauterivian; only a few of these continue into the Upper Cretaceous. When the Speeton assemblages are compared from an ecological point of view with communities living in modern seas, they are found to resemble most closely those of a land-locked gulf drawing its plankton, with some impoverishment, from the open ocean. Four new families, eleven new genera and forty-five new species are proposed.

In the course of a geological reconnaissance of Andros Island, in the Bahamas, it was found that the lower forms of plant life, especially the Blue-green Algæ, play an important part in the process of sedimentation. In addition to those forms which actively contribute calcium carbonate to the sediment, there are other species which function primarily as sediment binders, without necessarily precipitating any lime themselves. Such sediment-binding algæ usually impart characteristic structures to the medium in which they grow; and in the interior of Andros, where such deposits are now accumulating over large areas, structures are being produced which are reminiscent of those found in some of the great limestone formations of the Lower Palaeozoic and Upper Precambrian. In view of this, and of the supposed algal origin of certain of these limestone structures, it is felt that a detailed description of the Bahaman sedi- merits will provide an example of a modem Cyanophyceous deposit, which, may prove useful for comparison with older limestones of similar structure.

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In the spring of 1930 the International Expedition to the Bahamas made several traverses over the shoals west of Andros Island in order to study the sedimentation of calcium carbonate in this region, and along three of these lines water samples were collected at regular intervals. The chlorine content of each of these samples was determined by the author in the Chemical Laboratory at the University of Princeton, New Jersey, and the total salinity was obtained by calculation.

SummaryFour species of calcareous microfossils whose systematic position is unknown occur in very small numbers in the English Gault (Middle and Upper Albian). They are associated with much more abundant coccoliths, and are believed to be the hard parts of planktonic organisms whose possible relationships are discussed, but cannot at present be determined.