Generally the Ashiya group of the Karatsu coal-field and the equivalent Nishisonogi group of the Sakito-Matsushima coal-field are characterized by the intercalations of green glauconitic sandstone, while the Sasebo group overlying the Ashiya is characterized by the predominance of white micaceous quartzose sandstone (so-called "sugar sandstone"), and by lacking glauconite., In the north-eastern part of the Sasebo coal-field, the Sasebo group lies on the Ashiya with disconformity, or overlaps directly on the Mesozoic granite., In the vicinity of Imari, Arita and Haiki, however, the topmost part of the Ashiya, the Daito formation, about 250m., thick, consists mainly of the Ashiya-type shale with intercalations of the Sasebo-type sandstone, and the Sasebo group lies conformably over this transitional zone., The Ashiya group is subdivisible into five formations, namely the Kishima, Sari, Arita, Haiki and Daito in ascending order from a viewpoint of the cycle of sedimentation., The Nishisonogi group is also subdivisible into five formations, the Iefune, Nakaura, Okuura, Yuridake and Otao, and each formation is almost equivalent to each respective of the Ashiya group., These two groups have a general tendency, being usually rich in white tuff and tuffaceous rocks in the middle part., Furthermore, the cycle of sedimentation and rock-facies are common in the two groups on true whole., The correlation has been defined on those stratigraphic grounds., It should be noted that the Daito and Otao formations are those of the sedimentary basin, for the present distribution of strata is fairly continuous and in various localities they have much in common in rock-facies which indicates the Ashiya-Sasebo transitional zone as mentioned above.,