The Kingshill Limestone and younger carbonate rocks constitute the central portion of St. Croix, forming the remains of an ancient seaway that was flanked by emergent highlands. The seaway has been filled with thick epipelagic sediments alternating with carbonate turbidites and ash falls and capped with shallow-water reefal and terrigenous debris. Planktonic foraminifera indicate that ages of these rocks range sequentially in a SW direction from the middle Miocene to lower Pliocene. Scanning electron micrographs illustrate 42 species and subspecies of pelagic foraminifera and 13 selected paleoenvironmentally significant aberrant forms.-from Author