284 MYRIOZOID^E. 



SCHIZOTHECA FI8SA, Busk. 

 Plate XLI. flg. 1-3. 



I.KPRAUA FISSA, Busk, Quart. Joum. Micr. So., Zoophytol. iv. 308, 309, 

 pi. ii. figs. 8, 9, 10. 



Zocecia lozenge-shaped, smooth and glassy, disposed in 

 regular linear series, divided by deep furrows, and 

 radiating from a common centre ; orifice orbicular, 

 much raised, tubular, with a deep notch on the lower 

 margin; oral spines six, long and slender; avicularia 

 large, with a pointed mandible, generally directed out- 

 wards, placed at the upper end of a distinct area, dis- 

 tributed irregularly over the colony. Ocecia globose, 

 prominent, smooth or slightly roughened, with a large, 

 wedge-shaped fissure in front; two spines visible in 

 front on each side. 



Colonies forming small silvery-white patches. 



RANGE OF VARIATION. The avicularia are usually to be 

 met with near the margin of the colony, where they often 

 alternate with the ordinary cells. Sometimes they are 

 ranged in a line, with perfect regularity, amongst the 

 latter; not unfrequently there is a large collection of 

 them at a certain point, whilst few are found in other 

 parts of the colony. In some cases they are scattered 

 irregularly in the interstitial spaces. They are of large 

 size, with a long, pointed mandible, which falls upon a 

 well-developed " beak," and are placed at the upper end 

 of a distinct, lozenge-shaped area, which in size and 

 general appearance corresponds with the normal cell. 

 Apart from these differences in the number and position 

 of the avicularia, this is a very constant species. 



In the earlier stages of growth, the cell is destitute of its 

 tubular peristome, and is slightly sinuated on the lower 

 margin. When old there is a remarkable change in the 

 appearance of the zoarium, the walls becoming thick, 



