Important Points to Remember of Phylum Mollusca

Classification of Animals Non Chordates of Class 11

  • Tridaena derasa posseses largest molluscan shell.
  • Ammonicera rota is smallest mollusc.
  • Eupyrene are small thread-like motile sperms, which are capable of fertilising ova.
  • Oligopyrene are large spindle-shaped, non-motile sperms, unable to fertilise ova.
  • During larval development of gastropods, visceropallium rotates anticlockwise through 180° from its initial position. This is known as torsion.
  • Umbo is the thickest & oldest part of shell of Unio.
  • An organ which is used to transfer the sperms to the female body is known as intromittent organ.
  • Architeuthis posseses largest eye.
  • Octopus apollyon is the largest Octopus.
  • Tethys is the largest snail.
  • Architeuthis (giant squid) is largest invertebrate.
  • Helix alpersa is slowest moving snail.
Common Name
Chiton Sea mica (Mail shell)
Dentalium Tusk shell


Patella Limpet
Fissurella Key–hole limpet
Trochus Top shell
Pila Apple snail
Crepidula Slipper shell
Cypraea Cowrie
Natica Star shell
Buccinum Whelk
Doris Sea lemon
Aplysia Sea hare
Turbo Cat’s eyes
Vermetes Worm shell
Nassa Mud shell
Conus Cone shell
Bulla Bubble shell
Helix Land snail
Limax Slug
Pteropod Sea butterfly


Mytilus Sea mussel
Spondylus Edible oyster
Pinctada Pearl Oyster
Pecten Scallop
Teredo Shipworm
Solen Rozor clam


Sepia Cuttle fish
Loligo Squid (sea arrow)
Octopus Devil fish
Spirula Spiral shell
Architeuthis Giant squid


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