COLLECTED IN THE MERGTJI ARCHIPELAGO. 



221 



Genus Sipunculus. 



Longitudinal musculature divided into 17 to 42 bands. Pour 

 retractors. Body without papilla?. Tentacles finger-shaped, or a 

 lobed membrane surrounding the mouth. One or several caeca 

 on the rectum. Hooklets wanting. One or two contractile sacs 

 accompany the oesophagus. 



Species large. In all seas. 



3. Sipunculus eobustus, Kef er stein. 



Sipunculus robustus, Keferstein, Beitrdge zur anatom. und system. 

 Kenntniss der Sipunculiden, Zeitschr.f. wiss. Zoologie, Bd. xv. 1865, p. 421 . 



Sipunculus robustus, Selenka, De Man, andBulow, Die Sipunculiden, eine 

 systematische Monographic, in Semper 9 s Reisen im Archipel der Philippinen, 

 ii. 4ter Bd. Erste Abth. 1883, pp. 97-99, Taf. xii. fig. 170. 



Two specimens, of 17 and 30 centim. in length, and nearly 

 1| centim. broad. 



4. Sipunculus pobeectus, sp. n. 



Two yellowish -brown specimens of 28 and 32 centim. in length 

 and 1J centim. broad. 



The internal organs were partially macerated. 



On examining the exterior the most obvious peculiarities were 

 the distinct transverse rings, whereas the longitudinal furrows 

 are only faintly indicated. Sclerorhynchus about 1 centim. 

 broad and thick ; thickly set with papillae as far as a narrow smooth 

 ring in front. Tentacles very numerous (about 120), about 3-4 

 millim. long and \ millim. broad, flattened or fluted. These ten- 

 tacles are arranged in 2 half-circles on the right and left of the 

 border of the mouth, so that there is a small free space on the 

 dorsal and ventral median lines. 



Body musculature strong. The number of longitudinal muscles 

 running from before to behind is 32 ; anastomoses rarely and 

 feebly occur. 



Four retractors of the introvert are of the usual length ; 

 the two ventral retractors a few millimetres shorter than 

 the dorsal. Each retractor rises from 3, 4, or 5 longitudinal 

 muscles. The retractors are free for their whole length, and 

 coalesce just before their insertion into the introvert. From 

 20-25 longitudinal muscles are found in the greater portion of 

 tbe anterior half of the body, and freely traverse its cavity. Their 

 thickness corresponds to that of the longitudinal muscles of the 

 body, or perhaps less ; some are as slender as threads. These free 

 " accessory muscles " apparently originate from the longitudinal 



