is a elongate pennate diatom is very common in sediments - the form apparently allowing the cell to penetrate through the pores of the sediments. Pennate diatoms are important in intertidal and illuminated subtidal sediments in marine ecosystems and primary producers. Pennate diatoms are capable of movement, relying on the raphe to produce thrust. Pennate diatoms are usually regarded as boat shaped, although some of the boats have very odd shapes. They can usually glide. Although enclosed in a siliceous shell, the shell of these rather delicate diatoms is flexible. The plastids contain chlorophylls a and c which gives the yellowy-brown colour. Phase contrast.