Recent Work in Palæontology

Abstract

C. D. WALCOTT, among his studies entitled “Cambrian Geology and Palaeontology,” treats of a “a pre-Cambrian Algonkian algal flora” (Smithsonian Miscell. Coll., vol. lxiv., No. 2, 1914).” The horizon is that which has yielded the famous crustacean remains known as Beltina danai The author urges that the: abstraction of carbon dioxide from water by the action of blue-green algæ and bacteria, such as Bacterium calcis of the Florida Keys, is a potent factor in the precipitation of oolitic and other forms of limestone, and he freely quotes recent work, such as that of E. J. Garwood, in support. He regards the dolomitisation of the older limestones that may have been formed in this way as a secondary feature (p. 96). The author's remarks, in answer to G. Abbott, contributed to NATURE of December 31, 1914, may imply some reconsideration of the part played by inorganic concretion in the structures here described as various species of Newlandia. Collenia (p. 98) becomes separated from Cryptozoon, the latter being regarded as appearing for the first time in the Cambrian period.