This looks like a Peneroplis plantus foraminifera. It was found at Pago Beach on the island of Guam. Image is magnified 40 times under a microscope which should equate to a 1 mm field of view.
Learn more at the Foraminifera blog: http://foraminifer.blogspot.com/2010/01/peneroplis-planatus-optical-image.html
Thanks to Pam for obtaining the specimen and Herb for the processed material.
Update: I found another one and here is its picture.