i6o 



ZOOLOGY 



The Gephyrea Achaeta include ten genera ; of these Phas- 

 colion and Phascolosoma occur in our seas, the former usually 

 making its home in the shells of dead molluscs, the latter 

 living at the bottom of the sea half buried in sand. 



largest genus of the class is Phymosoma ; it 



The 



Fig. 103.- 



-Semi-diagrammatio view of the right half of the head ot Phymosoma varians, 

 seen from the inner surface. 



contains twenty-eight species, which, with very few exceptions, 

 are confined to the tropics, in many respects it resembles 

 Phascolosoma, and, as its structure has been lately worked out, 

 it will form the most convenient type for description. 



