We report observations of isolated lenses of constant-temperature water embedded in the permanent thermocline in the Sargasso Sea. These features are observed to have vertical extents of ≲220 m horizontal dimensions of ≲65 km, and residence depths near 700 m. A dynamic model is constructed which permits balance among the pressure gradient. Coriolis, and cyclostrophic forces and maintains the lens against gravitational collapse. A results that anticyclonic rim velocities approaches 20 cm s-1 are permitted and that these eddies have finite radii of the order of 50 km, at which their thicknesses fall to zero.