MUSEUM OF COMPARATIVE ZOOLOGY". 



299 



of two rows of alternating zooids, the tests are flattened at the 

 points where they come into contact with each other, and the surface 

 is therefore composed in part of flat facets and in part of curved sur- 



faces ; and at the point where two zooids are in contact a spur, or 

 diverticulum, from the outer tunic of each projects through the test, 



