The odontophore is powerfully developed; the radular sac is extraordinarily long, lying coiled in a space between the mass of the liver and the muscular foot.
The odontophore also is remarkably developed, its lateral teeth being mobile, and it serves as an efficient organ for attacking the other pelagic forms on which the Heteropoda prey.
In deed, were it not for their retention of the characteristic odontophore we should have little or no indication that such forms as Phyllirhoe and Limapontia really belong to the Mollusca at all.
The interesting little Rhodope veranyii, which has no odontophore, has been associated by systematists both with these simplified Opisthobranchs and with Rhabdocoel Planarians.
(16) P. Geddes, " On the Mechanism of the Odontophore in certain Mollusca."
Hubrecht in 1881 of a typical molluscan radula and odontophore in a new genus Proneomenia, allied to Neomenia, showed that the whole group belonged to the Mollusca.