POLYCHAETE WORMS, PART 1 187 



Ventral part of first five segments modified to permit passage of tlie 

 large muscular proboscis, with muscular gular membrane folded and 

 tucked within the lateral lips of the mouth. 



Parapodia (fig. 51) biramous, with rami well separated, with 

 acicular lobes flattened anteroposteriorly (supported by internal 

 aciculum which may have tip curved or covered b}^ pigmented 

 chitinous plate) and bearing fan-shaped preacicular and postacicular 

 groups of setae, with or without anterior and posterior lamellae 

 (flattened plates anterior and posterior to the setae), usually with a 

 curved ciliated branchia (sometimes referred to as interramal cirrus) 

 between the rami on a certain number of segments. Branchiae may 

 be cirriform, siclde-shaped or foliaceous, involute (curved inward, 

 fig. 48) or recurved (curved outward, fig. 51). Dorsal cirri (sometimes 

 referred to as branchial cirri) on the lower sides of the notopodia; 

 ventral cirri on the lower sides of the neuropodia; dorsal and ventral 

 cirri short, conical or foliaceous. Setae simple, cross-channeled or 

 camerated, serrated, ending in fine capillary tips; some may be 

 bifurcated (lyrate). Pygidium with a single anal cirrus. 



Proboscis (fig. 496) eversible, cylindrical, strongly muscular, 

 bearing terminally soft papillae around the opening, usually ten pairs 

 bifid papillae and two vertical lips, with a single middorsal and 

 midventral papilla. Usually subterminal soft, conical papillae 

 arranged in 14-22 longitudinal rows, with or without a longer 

 middorsal or midventral papilla between the terminal and subterminal 

 papillae. Basal part of proboscis smooth, ridged, or furnished with 

 low tubercles or warts. A pair of horny hooked jaws within the 

 proboscis, not visible unless dissected. 



All the species in the family bear a superficial resemblance, as- 

 sociated no doubt with their living in a more or less uniform habitat. 

 They burrow in sand, mud, or ooze from high intertidal levels to 

 great depths. They are prominent members of shallow water and 

 shore fauna. They are predatory and extremely lively and move 

 rapidly. They are able to burrow rapidly in moist sand, but do not 

 form permanent burrows. They swim by arapid undulatory movement 

 in a horizontal plane (they are referred to as shimmy worms). 

 They may leave the substratum for spawning and other excursions 

 and are active swimmers. In France, they are used as bait. They 

 are sometimes called sand worms because of their frequent occurrence 

 in sand. They are usually pearly or slate gray in life, with red 

 middorsal blood vessel, red branchiae, red midventral streak (neural 

 vessels lateral to ventral nerve cord; for details of blood vascular 

 system of Nephtys, see Clark, 19566). 



The parapodial cilia have been studied by Coonfield (1931, 1934). 

 The cilia on the parapodia are grouped into small tufts, in a single 



569-457—63 13 



