426 GEPHYREA chap. 



produced into a corneous spike. Six pinnate tentacles encircle 

 tlie mouth. Four retractors. Hooks present on the introvert. 

 Longitudinal muscles continuous. Intestine not coiled through- 

 out in a spiral nor fastened posteriorly. Spindle muscle present. 



8. Golfingia 



IV. No tentacles, but two leaf-like extensions of the body- wall guard the 



mouth. Four retractors. Few intestinal loops, quite free. No 



vascular system. . . . .9. Petalostoma 



V. No tentacles, no vascular system. One retractor, and one segmental 



organ. 



A. Introvert long. Body small, pear-shaped. . 10. Onchnesoma 



B. No introvert (?). Body cylindrical, thickly covered with papillae, 



which are larger and more crowded at both ends of the trunk. 



11. Tylosoma 



Species of Sipunculoidea. The genus Phymosoma (Fig. 214) 

 contains more species than any other genus of Sipunculoidea, and 

 they are all of fair size. Twenty-seven species are known, of 

 which seventeen occur in the Malay Archipelago, thirteen being- 

 found there alone. Phymosoma affects shallow water, the deepest 

 specimens being taken at a depth of about 50 fathoms ; this 

 may be due to the fact that they flourish only in comparatively 

 warm water. With very few exceptions, they are found only in 

 tropical seas, very often living in tubular excavations made in 

 soft coral rock. 



The genus Sipunculus contains sixteen species. They are the 

 largest and the most conspicuous members of the group. They 

 have a very wide distribution, some species, as S. nudus . (Fig. 

 212) and S. austmlis, being almost cosmopolitan. They are 

 most common in temperate and tropical seas, but S. norvegicus 

 and S. priajouloides are found far north, but always at consider- 

 able depths, 100 to 200 fathoms. 



The following account of the habits of Sipunculus gouldii is 

 taken from Mr. Andrews' 1 paper on that species: 



" This Sipunculus is very abundant in certain small areas of 

 compact, fine sand darkened by organic matter and not laid bare 

 at ordinary low tide. In such places, only a few square metres in 

 extent, they pierce the sand in all directions to a depth of more 

 than half a metre, making burrows with persistent lumen run- 

 ning from the surface downward and then laterally, but with 

 no regularity in direction. 



"Kept in aquaria, the dependence of the animal upon the 

 1 Stud. Johns Hopkins Univ. vol. iv. 1887-90, p. 389. 



