The dispersal of larvae over long distances depends upon the velocity of ocean currents and the duration of planktonic development. Plankton collections made throughout the tropical Atlantic show that the larvae of shoalwater spp from the continental shelf are regularly carried for long distances, and that they can be found in every major ocean current. The larvae of stenothermal tropical forms are carried westward from West Africa on the North and South equatorial currents and eastward from Brazil along the equatorial undercurrent. The gen Bursa is an interesting example, as its teleplanic forms are commonly found in both the tropical surface and undercurrent systems. An estimate of the duration of larval life and a knowledge of the current velocity suggest regular exchange of Bursa larvae between the continents of South America and Africa.