﻿SIPUNCULID WORMS OF CALIFORNIA — ^FISHER 375 



b^. Tentacles few to very luiinerous, arranged in a circle (interrupted dorsally), 

 enclosing nuchal organ and situated dorsal to mouth; longitudinal 

 muscle layer of trunk divided into separate anastomosing bundles; 

 retractors 4, rarely 2; skin covered with papilliform glands which some- 

 times become tubercular in anal region and at posterior extremity. 



Phascolosoma « Lcuckart, 1828 (p. 422) 

 fl2. A specialized shield or cone present at anterior end of trunk. 



b^. A horny or calcareous shieldlike structure present at both ends of trunk; 

 introvert arises on ventral side of anterior shield; longitudinal muscle 

 layer continuous, or divided into bundles Aspidosiphon Diesing, 1851 



b"^. A hard, calcareous, cone-shaped appendage ])resent at anterior end of 

 trunk ventral to which is introvert; no posterior shield. 



Lithacrosiphon Shipley, 1902 



b^. A round caplike structure made up of calcareous plates present at anterior 

 end of trunk, from center of which the introvert is extruded; no posterior 

 shield Cloeosiphon Grube, 1868 



Genus SIPUNCULUS Linnaeus 



Sipunculus Linnaeus, 1766, p. 1,078. (Type, S. nudus Linnaeus.) 



Diagnosis. — Usually large species with long cylindrical body and 

 short, sharply differentiated introvert covered with squainiform 

 papillae. Trunk generally thick walled, and longitudinal and circular 

 muscle layers divided into regular fascicles. Skin divided into rec- 

 tangular areas by longitudinal and circular furrows. Posterior end 

 of body rounded or bluntly pointed and sometimes marked off from 

 maia trunk by a limiting ring fold of skin. A flat tentacular fold 

 surrounds oral disk and from its margin tentacles of varying com- 

 plexity develop. No hooks on introvert or papillae on the trunk. 



Description. — The longitudinal muscle bundles rarely anastomose. 

 Characteristic of the genus are longitudinal integumentary canals 

 corresponding to the intervals between the muscle bundles and com- 

 municating with the coelom by slits between the regular circular 

 fascicles of muscles that are external to the longitudinal. The canals 

 contain coelomic fluid and anything floating in it. Retractor muscles 

 four, separated to head; nephi'idia two; spindle muscle present or 

 absent; a dorsal and a ventral contractUe vessel without appendages; 

 especially characteristic is an accessory intestinal spiral (pi. 18, fig. 

 1, A) between the end of esophagus and the beginning of the true 

 spire, and coiled in the latter. Esophagus and intestine anchored by 

 very numerous fixing muscles. "A median-dorsal unpaired epithelial 

 tube opens upon the sm-face of the head immediately behind the 

 tentacular fold, and leads backward to a cerebral sense organ anterior 



* The genus erroneously called Physcosoma Selenka, 1897. 



