256 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iob 



covered by a thick, channeled, heavily calcified frontal wall that 

 hides all zooecial boundaries. The thickness of this wall is 0.230- 

 0.504 mm. (average 0.334 mm.). The pores seen on the internal sur- 

 face of the colony frontal (pi. 12, H) do not correspond in position 

 to the pores seen on the external surface (pi. 12,B). The closely 

 spaced frontal pores (pi. 12,B) are the external terminals of the chan- 

 nels (pi. 12,J). The internal pores (pi. 12,H) are the internal terminals 

 of some of the channels. The channels diminish or deviate in their 

 course (pi. 12, J) so that a good part of the internal frontal wall is 

 imperforate. 



Because external boundaries of zooecia are lacking, external 

 measurements are somewhat approxunate; nevertheless, measure- 

 ments of zooecial length were made from orifice to orifice in a vertical 

 series. By this method zooecial length was 1.37-2.02 mm. (average 

 1.65 mm.). These compare closely with the fewer measurements 

 made on the internal surface of zooecia. Zooecial width (distance 

 between the lateral walls) based on internal measurements was 

 0.302-0.389 mm. (average 0.363 mm.). Zooecial thickness (distance 

 from the back wall to the external frontal surface) was 0.677-1.094 

 mm, (average 0.857 mm.). The side and back walls of zooecia are 

 very thin, ranging from 0.007 to 0.022 mm. (average 0.014 mm.). 

 The back walls are long, narrow, and nearly rectangular. The side 

 walls are wider (pi. 12, 1, J) and provided with bordering rows of 

 single pores (pi. 12,H) and a few more medianly placed multiporous 

 rosette plates (pp of pi. 12,1). The end wall is of variable thickness. 

 Its edges are thicker than the multiporous central part (pi. 12,I,J 

 and sp of pi. 12,J). Two irregular, heavily calcified processes (pi. 

 12,1 and pi. 12,K) slant a bit over this proximal wall sieve plate. 

 Their function is not known but it is possible that they serve for 

 muscle attachment. 



Avicularia: The internal avicularium is well hidden. It is not 

 visible from the outside because of its low oblique position inside the 

 zoid (pi. 12,D,H,I). It is placed below the side and corner of the 

 orifice. Its pointed, curved beak points obliquely upward away 

 from the frontal (pi. 12,E). It is on the side diagonally opposite the 

 external avicularium. For example, if the internal avicularium is on 

 the left side of the midline the external avicularium would be on the 

 right, and vice versa (pi. 12, D). This condition and arrangement is 

 found also in C. roydsi. Dimensions of the internal avicularia of 

 C. margueritae: total length 0.187-0.230 mm. (average 0.204 mm.); 

 total width 0.101-0.158 mm. (average 0.127 mm.); beak length 

 0.115-0.144 mm. (average 0.138 mm.); m,andible length 0.108-0.130 

 mm. (average 0.117 mm.); mandible width 0.094-0.115 mm. (average 

 0.103 mm.). The total length and width and beak dimensions are 

 based on only seven readings each, the mandible length on five and its 



