SIPUNCULIDA 



275 



Fig. 445 Sipunculus 

 nudus anterior end of 

 body with the introvert 

 extended (Ward). 



S. cumanense ( Kef er stein). Longitudinal muscles 21; body cavity 

 divided by septa into regular subdivisions as in an annelid; oral tentacles 

 present: North Carolina; Florida; Philippines. 



3. PHYSCOSOMA Selenka. Body covered with 

 papillae; usually 4 retractor muscles; introvert 

 with hooks arranged in rings; tentacles numer- 

 ous, not surrounding the mouth but lying above it, 

 forming a horseshoe; longitudinal muscles as in 

 Sipunculus; eye spots present: about 27 species, 

 mostly tropical. 



P. agassizi Keferstein. Body up to 4 cm. 

 long and 10 mm. thick; introvert as long as 

 body; about 20 rows of broad hooks just back 

 of tentacles, of which there are 20; 25 longi- 

 tudinal muscles: Pacific coast, Vancouver to 

 Panama. 



4. PHASCOLOSOMA F. S. Leuckart. Longitu- 



dinal muscles usually not split up into bundles but 

 forming a continuous sheath; mouth surrounded by 

 one or more concentric circles of finger-shaped ten- 

 tacles; 2 or 4 retractor muscles in the introvert: 

 over 25 species, cosmopolitan, some species living 

 in the shells of snails. 



P. gouldi* (Pourtales) (Fig. 446). Body with 

 longitudinal muscles not forming a continuous sheath 

 but split up into about 30 anastomosing bundles; 

 length 18 cm., the anterior quarter of which is pro- 

 boscis; skin smooth; tentacles very numerous, in sev- 

 eral rows; a pair of pigmented ocular tubes open 

 into the cerebral organ : Long Island Sound to Massa- 

 chusetts Bay. 



P. eremita (Sars). Body with transverse ridges, 

 2 to 5 cm. long and 5 to 12 mm. thick; introvert 

 nearly as long as body, without hooks; 2 retractor 

 muscles; no spindle muscle; 20 to 40 tentacles: 

 Massachusetts coast northwards, in 40 to 1,000 fath- 

 oms; Arctic Ocean. 



5. PHASCOLION Theel. Small forms living in 

 tubes or in small shells; tentacles numerous, form- 



* See "Notes in the Anatomy of the Sipunculus gouldii Pourtales," by E. A. 

 Andrews, Stud. Biol. Lab. Johns Hopkins Univ., Vol. 4, p. 389, 1890. "The Develop- 

 ment of Phascolosoma," by J. H. Gerould, Zool, Jahrb. Abt f. Anat., etc., Vol. 23, 

 p. 77, 1906. 



Fig. 446 Dissec- 

 tion of Phascolosoma 

 gouldi (Kingsley). 1, 

 mouth ; 2, anterior 

 retractor muscles ; 3, 

 intestine ; 4, neph- 

 ridium ; 5, posterior 

 retractors ; 6, gonad ; 

 7, nerve chord ; 8, 

 anus. 



