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 . They are cylindrical worm-like animals, with a median anterior mouth quite devoid of any armature or tentacles . The body is ringed, and often has circles of spines, which are continued into the slightly protrusible pharynx . The alimentary canal is straight, the anus terminal, though in Priapulus one or two hollow ventral diverticula of the body-wall stretch out behind it . The nervous system, composed of a ring and a ventral cord, retains its Q primitive connexion with the ectoderm . \ There are no specialized sense-organs or vascular or respiratory systems . There is a wide body-cavity, but as this has no connexion with the renal or reproductive organs it cannot be regarded as a coelom, but probably is a blood-space or haemocoel . The Priapuloidea are dioecious, and their male and female organs, which are one with the excretory organs, consist of a pair of branching tufts, each of which opens to the exterior on one side of the anus . The tips of these tufts enclose a flame-cell similar to those found in Platyhelminths, &c., and these probably function as excretory organs . As the animals become adult, diverticula arise on the tubes of these organs, which develop either spermatozoa or ova . These pass out through the ducts . Nothing is known of the development .

There are three genera: (i.) Priapulus, with the

species P. caudatus, Lam., of the Arctic and Antarctic and neighbouring cold seas, and P. bicaudatus, Dan., of the north Atlantic and Arctic seas; (ii.) Priapuloides australis, de Guerne, of the southern circumpolar waters; and (iii.) Halicryptus, with the species H. spinulosus, v . Sieb., of northern seas . They live in the mud, which they eat, in comparatively shallow waters up to 50 fathoms .