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.