This high resolution micrograph may show important features involved in calcareous plate formation within the alveoli that underlie the plasma membrane in Coleps. Densities are seen on the inner alveolar membrane at its corners with septa. These densities are not known at this time in other ciliates and may be involved in calcareous platelet formation within the alveoli or in stabilizing the surface shape. Filamentous material fills the cytosolic space between two densities. Densities occur at the corners of the alveoli with the cytosol. A Golgi complex lies next to this quartet of densities. Smooth spongiome is also observed. Microtome sections prepared at approximately 75nm thickness. TEM taken on 5/23/69 by R. Allen with Philips 300 operating at 60kV. Neg. 18,500X. The raw film was scanned with a Nikon Coolscan 9000ED. This high resolution image is suitable for quantitative analysis. Additional information available at (http://www5.pbrc.hawaii.edu/allen/).