Bile salts of the lungfishes Lepidosiren, Neoceratodus and Protopterus and those of the coelacanth Latimeria chalumnae Smith.

1. Bile salts of the coelacanth Latimeria chalumnae Smith (five specimens) and of the three living genera of lungfish (Dipnoi) were examined as completely as possible and compared. 2. The small 'bile acid' fractions include no more than traces of well-known C27 or C24 acids (free or conjugated) and the functioning bile salts must be regarded as alcohol sulphates. 3. Comparison of the alcohols suggest that (a) Latimeria stands biochemically outside the animal group which includes the Dipnoi, (b) Protopterus and Lepidosiren are more closely related to one another than either is to Neoceratodus, (c) all four primitive osteiychtheans have some amphibian affinities, (d) there are affinities between Latimeria and Dipnoi and ostariophysan families (especially Cyprinidae and Catostomidae) and (e) there are biochemical links between Dipnoi and lampreys.