The fossil vertebrate remains from "Het Gat", a site on the bottom of the North Sea, between the United Kingdom and the Netherlands, are described. This site is a maximally 46 m deep gully that cuts through layers of Holocene and Eemian sediments and reaches into the Yarmouth Roads Formation. This part of the Yarmouth Roads Formation is a complex of fluvial sediments of late Early-Pleistocene age, most probably Bavelian (a stage formed 1.000.000 - 750.000 years ago). The fauna is because of this attributed to a late Early-Pleistocene age; we correlate it to localities such as Untermassfeld (Germany) and Saint-Prest (France), which both have an estimated age of 1 Ma. The faunal content of the site "Het Gat" is provisionally as follows: Proboscidea Mammuthus meridionalis and/or Mammuthus trogontherii Artiodactyla Hippopotamus antiquus Alces latifrons Megaloceros dawkinsi Megaloceros savini Eucladoceros ctenoides Bison menneri Perissodactyla Equus major Stephanorhinus etruscus Carnivora Homotherium cf. latidens Ursus cf. etruscus These finds necessitate us to discuss whether or not two different species of mammoth can have coexisted and can thus be present in one fossil faunal assemblage. There appears to have been a continuous evolutionary development leading from Early-Pleistocene M. meridionalis to Late-Pleistocene and Holocene M. primigenius. Most authors recognize an intermediate species M. trogontherii, of supposedly Middle-Pleistocene age. The differences are in the dentition, while postcranially the taxa are difficult to distinguish. The molars we found in "Het Gat" can either be interpreted as advanced M. meriodionalis or as M. trogontherii. Until the taxonomy of Pleistocene Mammuthus species is clarified we doubt the presence of two species in one locality.