The Sambagawa and Mikabu systems are two important formations in the Japanese islands which have long been believed to reveal independent stratigraphic units among the older formations., The former consists of various crystalline schists, while green schits, or so-called "clastopyroxenite" by KOTO, are the leading members of the latter, to which several other metamorphosed rocks are found associated in one system., Because of barren of fossil the stratigraphic positions of these systems have been laid on the debatable ground., The current opinions on the moot question which have so far been established by Japanese geologists may be classified into the following three : a., The Sambagawa, Mikabu and Titibu systems are successively disposed in an order of geological age, among which the last one is the oldest fossillferous formation in Japan, and accordingly the other two below the Titibu must be pre-Carboniferous., b., The three systems are in the same order mentioned above, but they are separated from one another by two unconformities., Because each unconformity implies tremendous time-gap, the age of the Sambagawa could be as old as pre-Cambrian., c., The sambagawa and Mikabu systems are nothing but the metamorphosed Titibu system., Lately the writer made a renewed study on the sambagawa and Mikabu systems in the northeastern part of the Kwanto Mountainland where the systems are typically developed., As his results are summarized below, he came to the conclusion which is different from all of those opinions referred to above., Untiring effort of the writer for the determination of their geological agds was frustrated with the find of the fact that the two systems are in tectonic contact with the Titibu, wherever they are found together., More precisely, the Sambagawa and Mikabu systems apparently capping the Titibu in the surveyed area are in fact the Nappe of the two systems upon the Titibu., Moreover, the sambagawa system, in so far as can be seen, merges with the Mikabu and no definite boundary can be drawn between., The superposition of the Mikabu on the Sambagawa system may be a general status, but the reverse relation is met with at some places and a part of one system is in the heteropic relation to another part of the other system., Therefore the view of the two systems as independent stratigraphic units established by previous works no longer possesses raison d'etre., Furthermore, these formational names simply imply the metamorphosed facies of one or more formations., In other words, Sambagawa and Mikabu cannot stand as names of independent stratigraphic units., However, it is advisable that such classical names as Sambagawa and Mikabu are applicable to designate these kinds of metamorphosed facies, as the Ryoke metamorphics are used by the Japanese geologists in a similar way., As has been reported lately, the writer diseovered Radiolarian remains in certain parts of the Sambagawa metamorphics., Judging from these Radiolarians, it is certain that the fossiliferous rocks are Jurassic., On the other hand, it should be noted that the original rocks of the Sambagawa and Mikabu metamorphics are as a whole more allied to the assemblage of the Titibu rocks than to that of the Jurassic rocks in the Kwanto Mountainland., Bringing these evidences together, the writer led at length to the contention that both of the Jurassic and Titibu systems are comprised in the Sambagawa and Mikabu complexes, and that, if the two complexes are tied up in one, it reveals the metamorphosed facies of a series of formations ranging from Carboniferous to Jurassic., For this the writer intends to propose "Nagatoro system, " because the system bears not only a profound tectonic meaning but distinguishing petrographic characteristics, although several stratigraphc questions still remain unsolved. [the rest omitted]