The brown, rounded seeds were radish seeds, Raphanus sativus, and the oval, spiky seeds were carrots, Daucus carota subsp. sativus.
By the way, this seed mixture works well when planted together in a row or square. The radishes germinate and grow quickly, whereas the carrots are much slower. Pulling out the radishes as they are ready allows the carrots plenty of room to develop their own roots in their own time.