BBYOZOA. 319 



Lastly in Amplexopoia, cingulata, A. robust a, and other 

 forms, we have certain structures which may be peculiar modi- 

 fications of the ordinary cystiphragms. These occur in the tubes 

 near the surface of the zoarium. In vertical sections of these 

 species (fig. 7d) the first or innermost appears as two convex 

 lines which spring out from each wall and extend about one- 

 third of the diameter of the zooecium into its cavity. Above 

 these another pair of convex lines run parallel with the outer 

 half of the first pair, and after approaching each other quite 

 closely form a tubular prolongation, which extends some dis- 

 tance down into the space between the first pair. In tangential 

 sections they appear in the zooecial cavity as too circular lines, 

 of which the larger one encloses the smaller. From these ap- 

 pearances, it is clear that the first was of hour-glass shape, and 

 the second funnel-shaped. 



At the present time I am not prepared to offer a satisfactory 

 explanation of the cystiphragms. I may be permitted, however, 

 to suggest that they were in some way connected with the re- 

 productive functions. 



VIII. Lunarium This important character, with slight 

 modifications, is found in the CERAMOPORIILE, CYSTODICTYONID.E 

 and most of the FISTULIPORID.E. In its typical and most com- 

 mon form it is a more or less nearly semicircular portion of 

 the posterior half of the zooecial walls. The ends of the semi- 

 circle or crescent project into the zooecial chamber to a variable 

 degree, depending upon the comparative length of the radii, 

 being greatest when the radius of the semicircle is shortest. 



