The pottery of northern Europe can be distributed into a few groups or general types, every one of which is wide-spread and fairly distinct, though mixture or combination of types is not uncommon, especially along the boundaries of distribution where two types meet. There is much difference of opinion and discussion concerning details, but general agreement as to fundamentals and essentials.[117] Intermediate or "hybrid" forms also occur. The classification is hardly natural and is responsible for much confusion and dispute. It can have only temporary and provisional value. These three groups are: 1. Banded pottery, _Céramique rubanée_, _Bandkeramik_. 2. Corded pottery, _Céramique cordée_, _Schnurkeramik_. 3. Calyciform pottery, _Vases caliciforms_, _Zonenbecher._ They differ mostly in ornamentation, but often also as distinctly in form. 1. _Banded pottery_ occurs all over Europe except northeast of the Oder, perhaps also in Great Britain. Its shape is usually that of a spheroidal gourd with the upper fourth removed; and its system of ornament may have been derived from the system of cords by which the jar was once suspended. Sometimes we find a low neck, rim, or collar around the large mouth. The ornament in what seems to be its most primitive form consists of lines marked in the clay, arranged parallel to one another in bands covering most of the body of the jar. These bands, either broad or narrow, run in a zigzag or saw-tooth pattern horizontally around the base. By doubling each saw-tooth we get a diamond-shaped area. Even this simple ornament admits of a large variety of patterns. But the bands may be curved instead of angular, forming scrolls, meanders, or spirals. Logically, these should represent the latest development of the type. But the spiral may yet prove to be actually older than the angle. The bands may be raised and projecting (Bosnia) or be merely painted on a flat, sometimes burnished, surface. The incised lines may be plain or filled with a white material (encrusted). The briefest consideration shows that we have here a very generalized type or group of types which made its first appearance in Europe on the lower Danube and then underwent development by simplification or sometimes, perhaps, by increased complexity, as it radiated from this centre, becoming more and more modified as it went westward or northward.