Planocarina marginata (Penard, 1902)
Diagnosis: shell is colorless, oval or pyriform, laterally compressed, composed mainly of oval or circular shell plates, often interspersed with small beads of organic cement; shell with a small lateral ridge that begins just posterior to the aperture; aperture oval and surrounded by a small but thickened lip.
Remarks: this species has a characteristic small lateral ridge, but the degree of development of this feature is not constant and probably indicates a wide range of variability. I have found P. carinata and P. marginata always together.
These shell has been build from xenosomes, like a fragment of a diatiom (left hand arrow), the spine scale of Euglypha acanthophora (upper arrow) and plate scales of an Heliozoon (right hand arrow).