Van Veen grab samples were examined to study the environment and history of deposition associated with the coral reefs at Anton Lizardo, Mexico. These are Recent reefs growing on a shallow marine shelf which was emergent until 9,000 to 10,000 years ago. There are eight larger reef structures which rise from depths of less than 25 fathoms. The reefs are elongate and parallel to the shoreline. Although there is some carbonate material in the inter-reef sediments, most of the sediment cover is terrigeneous sand and gravel. Most of these sediments appear to be pre-Wisconsin in age. They were probably deposited while the area was exposed to subaerial processes. The post-Wisconsin coral reefs contribute only a small part of the sedimentary cover, and present deposition from the Rio Jamapa appears to be minor.