The plates I—XI contain illustrations of all the skulls and horn-cores of Bovidae from the Quaternary of the Netherlands, brought together in the National Museum of Geology at Leyden, Holland. They were all photographed with the occiputs vertical or what is thought to be vertical. They are described in the same order as figured. On the plates I—V are represented the skulls and horn-cores of the domesticated cows. Four races are distinguished among them: the brachyceros-race (fig. 1—25), the frontosus-race (fig. 26), the primigenius-race (fig. 27—41) and the trochoceros-race (fig. 42—46). The brachyceros-skulls and horn-cores have the following characteristics: a sharp angle (30°—50°) between the plane of curvature of the horn-cores and the horizontal plane, cores that are curved in one plane, a sharp angle (about 70°) between os frontale and os occipitale, a small breadth of the os frontale (table 1, measurement 2: 137—145 mm), a small index 6 (table 1), small measurements 10, 15 and 16 (table 1), a large breadth to length-index of the os frontale (table 1, measurement 13), a small difference between the length (table 1, measurement 27) and the basal circumference of the horncores (table 1, measurement 26). Examples of typical representatives of brachyceros-cows are given by the figures 3, 6, 8, 9, 12, 13, 21 and 22. The skulls and cores of the figures 2, 4, 7, 15 and 24 show some affinity to the primigenius-race and those of the figures 1, 5, 10, 16, 17, 18 and 23 to the trochoceros-race. The basal parts of the cores of figure 26 are strongly curved backwards and the plane of curvature nearly coincides with the frontal plane. As the points of the horn-cores are missing, the determination is somewhat uncertain. It is, however, not impossible, that this skull belonged to a frontosus-cow. The skulls and horn-cores, which I believe that belong to the primigenius-race, have the following characteristics: the cores are (when the occiput is placed in the vertical plane) directed strongly upwards and are not curved in one plane; the min. breadth of the os frontale (table 3, measurement 2), the length of the forehead (table 3, measurement 10) and the breadth of the occiput (table 3, measurements 15 and 16) are larger than those of the brachy-ceros-cows; there is a large difference between the length of the cores (table 3, measurement 27) and their basal circumference (table 3, measurement 26). Examples of typical representatives of the primigenius-race are given by the figures 27, 28, 31, 33 and 34. The horn-core of figure 29 probably belonged to a young Bos primigenius. The skulls and cores of figures 30, 32 and 35 show some affinity to the brachyceros-race. The skulls and horn-cores of plate V are believed to be representatives of the trochoceros-race. They are characterized by an angle of 10°—20° between the plane of curvature and the horizontal plane, a curvature of the cores in one plane, a backward curving of the basal parts of the cores, a longer breadth to length-index of the os frontale (table 4, measurement 2), a length of the forehead (table 4, measurement 10) and a breadth of the occiput (table 4, measurement 15 and 16) which are larger than those of the brachyceros-race. On the plates VI—VIII are presented the skulls and horn-cores of Bos primigenius. Comparing the measurements (see table 5) with those of males and females, as given by Adametz, it is clear, that the skulls and cores of figures 47, 48, 49, 50 and 53 belonged to males and that of figure 51 to a female. Skulls and horn-cores of Bison priscus are presented on the plates IX—XI. Among them are distinguished two different races, Bison priscus longicornis Grom. (plate IX, plate X, fig. 62, 65, 66, 67 and plate XI) and Bison priscus deminutus Grom. (fig. 63—64). The first is characterized by a large and narrow skull with long and slender cores and with a breadth to length-index of the os frontale (table 6, measurement 13) of 133—147. A comparison with the measurements as given by Gromova makes it probable, that only the skulls of figures 60 and 63 are females whereas all the others belonged to males. Bison priscus deminutus (fig. 63 and 64) is characterized by a moderately sized skull with massive cores and with a breadth to lengthindex of the os frontale (table 6, measurement 13) of 124. The min. breadth of the os frontale (table 6, measurement 2) is only 267—286 mm. There is, however, some difference between the skull of figure 63 and the skull of figure 64. The first mentioned has a convex forehead with regular transitions in the cores; the cores are only feebly curved. This skull is supposed to have belonged to a female animal. The skull of figure 64 has a flat forehead sharply separated from the cores; the cores are much more curved. This skull probably belonged to a male bison. Table 7 gives a review of the stratigrapbical distribution of the Bovidae, here described. The specimens of Bison priscus from Bokhoven (fig. 61), Brummen (fig. 74) and Drempt (fig. 64) certainly belong to Würm Glacial and the others probably also. The specimens of Bos primigenius may be devided into three groups. Enterbroek (fig. 48) and Ammerozden (fig. 49) belong to the Würm Glacial. Lutterzijl (fig. 47), Nieuwe Merwede (fig. 50) and Terschelling (fig. 51) belong either to the Würm Glacial or to the Holocene. The others are holocene. Of these the specimen from Veghel, 2 m (fig. 54) belongs to the Boreal and those from the Mease-tunnel (fig. 52, 55, 56 and 58) and Dinther (fig. 53) to the Subboreal. The normalisation-works of the river Aa, Northern Brabant, have furnished some important data as to the stratigraphical distribution of Bos taurus. The oldest specimen, Veghel, 2½ m — (fig. 23), has been dated by pollen analysis as belonging to the upper part of the Würm Glacial, the so-called Lateglacial. However, it is not probable, that this horn-core is derived from a domesticated animal. The oldest occurrence of domesticated brachyceros-oxen are contemporaneous with the Kjökkenmöddinger culture (5000—4000 b. C.). The horn-core of Veghel, on the other hand, is of the same age as the late palaeolithic culture (before 8000 b. C.). Therefore it is much more probable, that the core belonged to a wild ox, namely Bos (Brachyceros) europaeus Adametz. By several investigators (Adametz, Antonius) this species is considered to be the wild ancestor of the domesticated brachyceros-oxen. The specimen from Veghel renders this theory more probable than the view advocated by Nehring, Duerst and Hilzheimer, who suppose, that all the races of Bos taurus, the brachycerosrace included, descended from Bos primigenius Boj. The first undoubted tame cows from the river-basin of the Aa are dated by pollen analysis as belonging to the transition from Boreal to Atlanticum. This is the beginning of the late mesolithic Kjökkenmödinger culture. The still persisting flint-industry (microliths) is associated with the first pottery. It is the time of beginning agriculture. As demonstrated by the finding of remains of Cervus elaphus L. and Bos primigenius Boj., the deer and the aurochs were formed the chief hunting quarry. In Subboreal time this district was inhabited by the so-called „urnpeople”, by who not only the brachycerosbut also the more robust primigeniusand trochoceros-cows were breeded. The district of the larger rivers is characterized by the absence of Bos taurus brachyceros, the probable presence of Bos taurus frontosus, during the Subboreal, and the presence of Bos taurus primigenius during the Boreal and Subboreal. The absence of the brachyceros-cow is probably imputable to a hiatus in the collections of the Museum at Leyden. Contrary to Bos taurus brachyceros, Bos taurus primigenius is generally considered to be a direct descendant of Bos primigenius. It is however not yet known at what time the first aurochses were domesticated. Without doubt the skull from Wijk-bij-Duurstede (fig. 27) belonged to an animal, that lived at the beginning of domestication. The frontosus-ox is not found among the fauna of the Swiss lake dwellings. However it is described by Degerbøl from the Subboreal of Denmark (Bundsø). Therefore it is probable, that the „urn-people” living along the large rivers had a different origin to the people dwelling in the sandy regions of Brabant.