THE GEPHYREA OF JAPAX. 31 



Habitat : Nalia on Okinawashima (one of the Islands of 

 Kiukiu), among dead coral masses. 



Genvs SIPUNCULUS. 



SIPUNCULUS NUDUS, Linné. 



Selenka, (28), 1884, p. 92. 



The main characters of this species are as follows : 

 Specimens from the Mediterranean Sea, according to Grube, 

 may be 2 feet in length, about 8 inches of which appertain to 

 the introvert. The latter is covered with an immense number 

 of large and very high papillse. The body proper shows on 

 the surface 30-33, mostly 32, longitudinal grooves, which by 

 intersecting the numerous circular grooves form small rectangular 

 areas. The mouth is surrounded by a tentacular membrane which 

 is divided into the dorsal and the ventral lobe, the former being 

 subdivided into large and the latter into small folds — the tenta- 

 cular flaps. 



The longitudinal muscles are divided into 30-33 bundles 

 which very rarely anastomose. Four retractor muscles arise at 

 the same level from the 4tli — 8th longitudinal muscles. On the 

 rectum are found a small diverticulum and two glandular struc- 

 tures, the " büschelförmige Körper." The spindle-muscle arises 

 slightly in front of the anus, and is posteriorly free from the 



