1. There are thin gill filaments on either side of the ctenidium . 2. Osphradium is narrow, positioned slightly posterior to middle of ctenidium . 3. The ctenidium , the respiratory gill-comb, is very broad. 4. Ctenidium is positioned a little in front of pericardium.5. At the posterior of the ctenidium is a remarkably large and well-developed heart. 6. The shells of these two last genera house a hypertrophied ctenidium large quantities of symbiotic bacteria. 7. This proportionally giant heart primarily sucks blood through the ctenidium and supplies the highly vascularised oesophageal gland. 8. The ctenidium ( a comblike respiratory apparatus ) goes along most of the length of the pallial cavity. 9. The gill is flaplike with a bipectinate ctenidium situated in the nuchal cavity and lacks secondary pallial gills. 10. A "'ctenidium "'is a respiratory organ or gill which is found in many mollusks.
