PRIAPULOIDEA, a small group of vermiform marine creatures; they have been usually placed in the neighbourhood of the Gephyrea, but their position is uncertain and it is doubtful if they are to be regarded as coelomate animals.
P. Lamarck's term Annelides, now used to denote a major phylum or division of coelomate invertebrate animals.
The Mollusca agree in being coelomate with the phyla Vertebrata, Platyhelmia (flat-worms), Echinoderma, Appendiculata (insects, ringed-worms, &c.), and others - in fact, with all the Metazoa except the sponges, corals, polyps, and medusae.
On the one hand the Turbellaria are considered to be an offshoot of the early Coelomate stock, on the other they are held to be descendants of a simpler two-layered stock.
This resemblance is considered by Hubrecht (5) to give reason for concluding that the Polyclads are an offshoot, and possibly a degenerate offshoot, from the early Coelomate stock.